The biggest issue would be housing while at home. I'm kind of surprised most teams just haven't built dorms for the players. Otherwise, food, travel, training in season are all paid for or available. The only other cost I could think of would be steroids.
It may be going that way now, 150 years later. It's probably gotten a little better, but most of my buddies that played in the minors ($850 a month for 5 months back then, no $$ in spring training) lived on PBJ, with occasional post-game pizza for bus rides. Host families were the thing then, and they have been fading fast. The families feed the players at home, but not all homes are alike, and there are tons of horror stories about bad situations happening. Imagine Annie's husband walking in on her and Nuke...
A big downfall is that guys that are used to having money spend it, and guys that never had it spend it. Six years to free agency, after you make the big leagues. That is where the money is. One of the first things I learned as a scout was when you ask what the goal is, if they say "play professional baseball", it's done. It's MLB or nothing...The bonus money is nice, but they all make the same when they put the uni on in the minors.
Scouts always laugh about going to spring training and the player's parking lot..you see a lot of hot, expensive older cars, who belong to career minor leaguers who were "going to the Show".
The fallacy that they are "all rich", or gonna be rich, because they are pros became laughable, once I was inside of it. Ball clubs want hungry players, and encourage the rough treatment as motivation to get out of there.
Truly survival of the fittest, and to the victors go the spoils...