Sorry about the break up and wishing you and your son the very best!

Is it really Unsafe? Is that repairable? What would it take to make it safe again? Often times that is an easier fix than buying a new vehicle. Esp if your current car is paid for and you are struggling for a down payment on the next car - car payments SUCK and end up being a long term drain on your finances, especially if you're already struggling.

Wanting a truck for side work is a different matter altogether. I've personally had luck with Carmax. However, if you really want to find the best possible deal - avoiding shops that advertise "BUY HERE PAY HERE" and charge ridiculous interest rates (again, borrowing from your future self) Many are collision rebuilts and junk from auctions; private party is the way to go.

Again, best of luck - Wishing you and your son the very best.