Anonymous wrote:OP I'm in my mid 30s but I drove a gently used, new-ish Mazda3 for most of my late 20s and loved it. You can get one used in good shape for ~10k and it will be safe and reliable, and you can trade it in for something bigger in a few years when you are ready to upgrade and know what you need. I held onto mine until I had my first kid and wanted a SUV.
I saw a lot of my friends go in the opposite direction and buy a fancy car that took up a big chunk in monthly payments, but for me being able to buy the car outright and not have the monthly payment gave me a lot of financial freedom at a time when I could make the most of it (the time to travel, savings towards retirement that have a lot more time to accrue interest, and no need to accommodate carseats or kid gear).
The market is so hot for used cars right now you cannot get a Mazda 3 for 10k, even with high miles. And I would not get a car with high miles, not worth the risk.
If I were you, I'd get a gently used car in the 10-15k range with low miles, put down 5k and finance the rest. Carvana has a useful search feature.
https://www.carvana.com/cars/filters/?cvnaid=eyJwcmljZSI6eyJtaW4iOjc5OTAsIm1heCI6MTUwMDB9fQ%3D%3D