It can be a wise investment to pay for the training yourself rather than just sit and wait. I fully understand your situation, you are getting older and you cannot live with your mom while working as an FI earning “peanuts”.
But buying an A320 or B737 isn't the solution, the odds are low that you will find a job with just 300TT and no hours on type= bad investment (unless you are lucky). If you buy line training as well the investment increases but the chances of getting a job afterwards is much higher, and then it could be worth the money.
A good investment is the one that gives you a job, and believe me, there are a lot of pilots with just a B737/A320 unemployed.
I suggest you first try the self sponsor routes with a job in the end.
Or take a look at the smaller aircraft like previous mentioned the ATR.
Or B737/A320 with hours on type.
Remember, there are no guarantees.
Good luck.