99-04 Mustang Worth Modding?

I could afford a house now but I don't want to committ to living here for more than a few years.

I'm not spending 50k+ on the car. Maybe 10k at most. That's 1/6th of my salary. I'm not going to squeeze every penny and not enjoy my hobby in the present just in the hope I get something some day that doesn't even ultimately matter a ton to me at the moment.