I've had the pleasure of buying and restoring several cool 90's cars. I thought I would document the process I go through.
I can't stress this enough. I would never jump on Craigslist and buy the first thing that pops up. I will join forums months (sometimes years) ahead of time. Forums often contain FAQ pages that I'll read through. Sometimes I'll just hit the "New Posts" button at the top and check it weekly, clicking on anything that looks interesting. I want to know what year(s) were the best, what the common problems are, what issues to look out for, what aftermarket stuff is the best/rare, what major parts are discontinued, what's the best/cheapest dealer people deal with for parts, what colors/options the car came in and get a general idea on what I'd expect to pay.
From there I'll make my decision. Typically I try to buy pre-96 to avoid the ODBII checks. I'll also decide on one or two colors I could live with. Mechanically I like to have the best year possible. For instance with the 3000gt I wouldn't buy a 91-92 as they have the weaker 18 spline trans/transfercase, as well as a weaker 2 bolt block. When looking at the RX7, the 94+ had the better interiors. The 93 had all the rubbery textured stuff that would get sticky and peel. I also like to know how much of a project I'm looking for. Are there pieces missing? Does it need new paint? Are all the exterior trim seals dried up and some discontinued? It's a lot easier for me to shop for something when you know a lot about them.
I will search daily everywhere. I'll check forums daily, Craigslist, Facebook Marketplace, and eBay. I'll do this even if I'm not financially ready to buy. Its good practice and helps me track the price of the market. It's also a good way to learn about what different modifications. If I see something that looks different or aftermarket and I don't know what it is; I'll research it. This is how I found out about BTI gauges for the Supra. Location isn't too big of an issue for me. Growing up in VT I realized that any car I want, probably isn't going to be anywhere near me. I've bought and driven stuff home from as far away as California.
I like to try and be financially ready to purchase anything. I'll either save cash up and/or be pre-approved for a loan. Surprisingly its not that difficult to get a loan on a 90's car. My credit union will actually finance up to 110% of value (they go by NADA) if you want, providing you have good credit. I'll contact the seller and ask them questions, specifically about the common problem areas I recently researched. I'll ask for pictures if enough weren't provided. I'll get the VIN# too and do a car fax. I won't buy anything that is a salvage title (well maybe theft recovery but that's it) or has been in a serious wreck. Since I have the VIN# I'll also Google it, and search for it on the forums. With my Supra I was able to find 4 prior sale ads going back 8 years.
Mileage is not a huge concern with me if the car is clean. The one thing I cannot stand is rust. It's not worth buying a Subaru with rusty quarter panels. I'll go down south, or out west if I have to, or hope to find one stored winters. I know the extra money I'll spend in travel/transportation will outweigh the cost of rust repair. Even if the car has had rust repair work done and it looks pristine from the outside, I still will not buy it. I want to start off with something that is clean at it's core. It will hold it's value better, I won't have to worry about rust eventually bleeding through, and I will grin every time I remove a 10mm undercarriage bolt and it comes out in one piece:)
When I look at the vehicle, I'll check everything. I'll look for overspray near the trim pieces to see if it's been repainted. I'll check all the gaps (especially near the quarter panel areas) to make sure nothing has been hit. I'll crawl under the front and rear of the car to inspect behind the bumpers. I'll make sure the lower radiator support is straight. I'll open the doors and shine a flash light behind the fenders. If I like the vehicle, I'll make it happen. If not, I will pass and move on. I've came home a few different times with an empty trailer. It sucks, but it is not the end of the world. Stop and get a nice dinner somewhere, make the best of it, then keep looking.
When I get the car home I'll look through the entire vehicle inside and out. I'll check the wheel bearings, tie rod ends, ball joints, sway bar bushings, endlinks etc... and take note of anything that is bad. I'll inspect every interior panel and look for anything that is damaged, missing or out of place. If there is a plastic cap that hides the head of a screw on the door panel I'm going to take note of it. If someone used a non factory bolt on something I'll write it down. If I find some change under the seat I'm going to pocket it and do some math in my head calculating how I really paid less for car.
From there I'll try to sort what's in my list. I tend to divide stuff into 3 categories:
Just to give an example of each... Stuff like faded/chipping wiper arms or rusty seat feet are something I can fix myself with some fresh paint. A torn shift boot or bubbled door panel is something I'd want to replace. A crumbling heat insulator shield that goes under the hood is something I'd just remove because it's not needed. Any maintenance part like a wheel bearing I'm going to go with an OEM replacement. Any small stuff like missing screws, or plastic caps I'll buy new. For larger interior panels it will depend on if the parts still available and how expensive it is. It's a common problem for 3000gt door panels to bubble in the armrest area. New they are $500. You can find used ones without bubbles for around $100 so that is the route I would take.
It does pay to shop around. My local Toyota dealer (Heritage Toyota) wanted $349 for an OEM rear wheel bearing for my Supra. I purchased the exact same part from EB Toyota a state away for $201 plus shipping. For parts no longer available, I'll try to source them on the forums or Facebook. For stuff that's hard to find, I'll check eBay and setup an alert on the part# if I can't find anything.
This is what I enjoy doing the most. I'll plan out what I want to do for suspension, radio, engine, drivetrain, and interior. Once I have my game plan in place I'll start buying parts. I don't have endless funds at my disposal so I try to make the most of my money. I do keep an eye out for used stuff or group buys. I also try to take advantage of vendor sales around the holidays. While I'm waiting for stuff to come in or saving up for more expensive items, I'll focus on taking care of the cheaper DIY stuff. There are a lot of improvements you can make to an older car for a little bit of money. Some sandpaper and spray paint can go a long ways. Here is some of the stuff I may do, depending on the car.
Here's something I fixed on my Supra. For some reason the passenger seat recline lever had 2 non-oem bolts holding it on. They were too long which caused the end of them to rub against the plastic trim piece on the side of the seat. I had 2 nice grooves cut into them. I was able to find the factory part# online only to learn it was discontinued. I checked the forum and was only able to find WTB ads for other people looking for the same part. I couldn't find anything on eBay, but I setup an alert anyways. I don't expect to find a replacement anytime soon. Even if someone did have this piece it would probably be part of a seat they are trying to sell. They aren't going to remove it and sell you the part individually. So I went at it with my plastic welder. I filled in the grooves, then lightly tapped it with the point of the welder to give it a textured look similar to the oem pattern. It's not perfect, but 10 minutes of my time definitely made this a lot less noticeable.
That about sums it up. Obviously every car will be a little different based on what it needs. Sometimes it does get a little repetitive (like repainting seat rail feet), but it needs to be done and I know the end result will look good. I do like when I run into challenge and am faced with something that I've never restored before. I'm awful about taking before pictures, but the next car I do I'll be better about it. That way I can come back here and ad some before/after pics.