Pictures are no way to buy a car for sure. The car always looks better in the pics that in person.
Gateway I do not respect at all. I use to travel quite a bit for work and looked at dozens of their cars they are never done right and are never as they state them to be.
Even when you do an in person inspection you need to know exactly what to look for. When they put up an ad and show nothing under the hood, interior, trunk or undercarriage you know there are issues.
You need to spend some time on the Forum and just observe, read and ask questions. The 71 -73 cars are much better than the earlier Mustangs I think. But as with any vehicle the models shake out in a pecking order. Some people prefer certain models and not everyone wants a Boss car. But this is a rough list of how the sell in the market.
1971 Boss 351 Concourse would probably be the most expensive.
1971 429 Mustang in Mach 1, Sportsroof, convertible or coupe bring good money if they have matching VIN# on drive train and body. Condition is everything. A rust bucket can never be made as good as a rust free low miles original car.
It could be a toss up between the Mach 1 and convertible but the higher end models both do well. By higher end that would be R code, M code, Q codes first. Then H and F codes and I would never even look at a 6 cylinder right now. We have members with inline 6 that love them.
1971 & 1972 have little more HP and some difference is due to the way they rated them. 1973 got the biggest hit by loosing the CJ 351 and loosing HP.
I like original cars for sure I have a couple with factory paint and interiors. One I drive a lot is a 1973 convertible the other is a 1973 Mach 1.
The options list for these years is very extensive so a car with lots of great options is a plus. Cars from New Mexico, Arizona, California usually have less rust. The other thing that rusted out these car was simply washing them. They were not dipped in primer just sprayed so lots of cracks had no protection so when you wash them you feed the rust.
Ruthless dealers will smear on the bondo and undercoat to hide cracks holes and do not care if they swindle you or not. You will always see the note on a Bill Of Sale "As is where is no guarantee". There is no recourse in or out of court if you accept those terms.
Most cars have the undercarriage just rattle can sprayed and no details. In this day and time it is pretty much impossible to restore a car to concourse condition and sell it for a profit. It is a labor of love.
Most of the cars you see on ebay are priced double what they are worth. When they sell if you click on the bidders you will usually find the winning bidder to be a joke bidder. Someone just on ebay playing and running up a bid and never closing the deal. They will have lots of retracted bids and bid on everything. Sometimes I think it is ebay trying to jack the prices up to get more money.
I have bought two cars off ebay and was happy with them. One was in California and one in Dearborn MI. I shipped the Calif. car and went and got the Mi. car. I have bought several that I found on Craigslist but you need to know what you are looking at. I asked for very specific pics of specific areas of the cars before I even bid.
You will see lots of failed restorations some can be good buys but some can be horrible and impossible to finish.
Go to shows and look at lots of cars and take pictures and ask lots of questions.
You can get a Marti Report for $18.00 in a few days on any Mustang from 1967 to now. It will tell you all about the car, what options were factory installed and where it was sold originally.
Do not be afraid to give a low offer and be prepared to walk away.
Education will save you more money than anything else you can do.
There is a Mustang show coming up in March there will be over 1,000 cars there in Sevierville, TN called Ponies in the Smokies. There will be an inside display with a Mustang for each year great place to find a car also. In April there will be National Mustang day at the Mustang Owner's Museum in Concord, N.C.. Last year there was over 1,100 mustangs there.