On the players' cost side of their equation.
The club provides uniforms. The player supplies cleats and gloves. For players cash strapped, their single pair of cleats gets pretty stinky as the season progresses; better off players have more shoes (an agent can help here). If you get traded, you need to buy a new pair of cleats if the color is wrong.
At the lower MILB levels, most clubs have "host family" options. But this is a term which connotes a soft fuzzy, all-providing, free experience. That may be true, but most likely not. At the collegiate level (think Northwoods and Cape) host families don't cost the player and may include a total commitment from the host family to care for the player for free (car, food, laundry, fishing, hunting, etc.).
In MILB, a host family is permitted to be paid. A maximum amount which can be charged (the club even handles the billing) is set; the host family is not required to collect that, but most do (there are very real costs in housing a player). I believe it is somewhere around $300 per month. It may include a car, laundry, and food, it may not. Because host families tend to be repeaters, the new players have some pretty good Intel on the conditions offered by the host families. The players go into this with eyes open. I have heard of players getting single rooms, cars, food, and laundry - like home; conversely, I have heard (straight from the host mom) that players can be crammed into bedrooms in multiple bunk beds (though they ate well). Some families look to this as income supplements, others don't. It is a very individual experience - but most of the time not free. (IMO, nor should it be.)
Some clubs with affiliates in high cost areas (think New York) effectively subsidize their players by using converted motels and charge players less then the free market rents would garner - but the cost is still roughly $300.
For players who live in more "commercial" settings (short term rentals), expenses quickly exceed their available funds. A player rents month to month, pays first month and a damage deposit. If you are the sucker who signed the lease, you're on the hook when a roommate is traded or moved. The rent is what the rent is - a player can take it or leave it; some players live six in a two bedroom place; some live a bit better. Furnished/unfurnished, it's up to the player. Clubs have a person detailed to help and players also have the advantage of prior players Intel. The players always make it work - though a player may who is moved may be paying for multiple places. (Many times, the moved player's replacement will take the spot; but that's up to the replacement player.)
The player pays, when home, his "clubbie". The clubbie works his butt off in doing laundry and post-game snacks. The amount per day increases at each MILB level (I have heard that MLB players pay $200/day to their clubbies). What the clubbie does with the money varies - some try to not spend it all on the players (and keep the difference); others reach into their own pockets to supplement the food purchases. Some go to the local low end supermarket and make PBJ sandwiches; others make magic with the money. At the lowest end the clubbie fee starts at $5/day. I have heard of full blown fist fights breaking out over players taking more then their share of post game food. Many clubs bring their organization clubbies to spring training for clubbie training.
Some clubs bring the left over ball park food for the players to eat. That varies in quality, quantity, and nutritional value. Occasionally, an MLB player is rehabbing with an MILB club and that player generally buys food for the rest of the club. (Just saw a tweet about Phil Coke buying food for Stockton.)
On the road, players get a per diem beginning at $20/day. Eat hearty, fellows! Hopefully the motel where you sleep has a big breakfast. Where clubs decide to commute (up to 99 miles as the crow flies), no per diem. Don't eat hearty, fellows! Food is always an issue with the players - never enough good food at the lower levels.
Take the hypothetical low level MILB player (full season A and below): gets roughly $1,100 per month beginning the day he is assigned to his club. After mandatory deductions (FICA and Medicare) he has $1,000 left. $350 in rent, $100 to the clubbie (15 days at home for a month), gets $300 for road meals (ignoring the 99 mile situation). Player has $850 per month (less the rent deposit) to eat, gas, laundry, etc. Income taxes are zero - but unless the player increases his exemptions (increasing his take home pay), income taxes are in fact taken out (leaving a new can of worms - filing for a refund - to be addressed by his parents). The clubs give no advice on the exemption issue, and most players don't catch this the first years.
Can a player live on this; certainly. Can a professional athlete eat food which maximizes his productivity; no. Can a player have a beer to unwind after a game within this budget; certainly - every single Saturday nite.
The cost side of the equation is a matter not subject to any federal or state rules; players know or should know (or have access to the information) these issues and prepare for it.
Can a player work in the off season? Yes, so long as the work isn't prohibited by his contract (e.g. Sky diving instructor, and other risky endeavors). Many traditional employers would prefer not to hire someone who will be leaving in a few months; some will. I know a player who worked as a constructuon flagman in the offseason - very high paying job. Many work in the industry - lessons, travel ball coaches, etc., which provides them with money to live (not so much to save though).
Can a player get unemployment compensation? This is a state by state question. Each state has different rules on eligibility, amounts, conditions, etc. I believe that California will not give UC to a player under contract (though I don't know if that decision was a court or administrative decision). And the original draft contract extends for many years.
The cost side of the equation is what it is - some guys live cheap and save their per diem for the casino; others save their money to try to focus on eating better.
The compensation side of the equation is subject to (or not, if MLB fits in an exemption) minimum wage rules.