With the cost of models being almost insane these days, I know that when I pay over $100 dollars for a kit, I'm not going to chance it. I do use 90% iso alchohol instead of Tamiya's thinner and do use a regular gallon of mineral spirits from Home Depot or Lowe.
I fully agree that the price of hobby paints is very high per volume, and seemingly rising.
I always buy white and black and other always needed colors online for maybe .80 cents to a dollar cheaper than the LHS, and never but never can buy a kit anywhere but online.
House paint probably would work.
Ross would be the one to ask.