Saying howdy, starting to research, thinking of a first gen

Welcome! Thumbsup for the Dave Ramsey plan, though don't put too much money into that Jag! Great idea, too, working on a Mustang with the boys. Good luck!

Welcome back into the mustang fold. My suggestions are:
Don't buy the first car you find, get the car in the best starting shape you can physically. Engine/drivetrain is the least expensive to repair/ replace, rust, bodywork and repaint are the $$$ items so if you find a car that is solid that needs mech. work go for that or a car that needs some work on the interior, drivetrain,et. but has recently had bodywork and fresh paint. You get the idea. A solid foundation is key as everything has to come off to fix that and takes skills to get right.

You should have a good selection to choose from as 6's and Coupes are not in high demand at the moment. Look for one with some options if you can or maybe a conv? Check your local CL and mustang sites like this in the classifieds section, also join or just attend your local mustang club meeting and put the work out you are looking for a nice '66 w/6. People in clubs are passionate about their cars and put more work/money into them than they know they will ever get out or they buy a project and give up.
good luck in your search,
Jon