Drunken Waffles
Depends on the kind of modding you want to do (performance vs visual, for example) along with your budget and the end goals you want to achieve.
Under $4,000, you're likely going to be spending money on routine maintenance and wear & tear items first.
Tim
I got a 1982 Buick Electra a old lancer would be nice to you'd have to tel me what brand you like