If you raise your own critters on 100 acres, get set into a rotational grazing system - that is the best way to up your income. It can take 5-10 years to get to a good working setup, but it is well worth it. Even just breaking your 100 acres into 4 padacks will go a long ways.
Renting out, a rancher will pay about 45 cents a day to feed their cow. So it depends on how much grass your land can grow. If you are in a dry area of the mid southwest, then $20 an acre might be about right. If you have rocky poorer soil, a little less might also be about right. I'd maybe look at customs in your area, learn who maintains the fence (you or the renter) and if pasture isrented by the animal unit per day, or on a yearly amount per acre. It is often better for the owner to rent on a per animal unit per day rate - this keeps your pasture from being overgrazed & ruined. If you don't have much to eat any more, the renter moves his cattle - they get thin & it's costing him every day. If you rent per acre; well if pastures get short the rener might just keep his critters stored ther, bring in a little hay to tide them over, and your pastures turn into grassless dust bowls. Lot of grey area between my extremes, just mentioning how the games work.
'Here' you can stock 2 cattle per acre from May - October. 'There' you might need 7 acres or more per critter? Growing grass all depends on how fast you can get grass to regrow, which totally depends on your soil quality/ fertility & how much rain you get.
Rotational grazing easily gains you 1/2 more critters on your land once a person has it set up & working & keeps up with moving the critters.
Corn: Works well to grow corn, if you have the rain & soil for it. I suspect you only have soil & weather conditions to grow grass? You have to work with what you have, I know 'here' I would rent it out for $250+ an acre to raise corn or soybeans. 'There' that likely won't work at all.

Of course 'here' you would be paying $4500 an acre to buy that land - you might not have invested that much?
Hay: If it isn't too rocky or steep or tree'ed; Works good, but you need a market to sell to, and making good hay takes some equipment and being _very_ on time cutting, raking, baling, and stacking the hay. No - get around to it in 2 days....' Then you will be making poor hay, and you lose any chance at making money at it. Hay = being very on top of the clock & doing things now when needed. Waiting even 3 hours to go rake hay can lose you all your profit on that hay.....
Profit from cattle: Oh boy!!!!

Cattle prices go in cycles. Sometimes you lose money for 5 years straight, then hit it big in one year make it all back plus some to do it again for another 5 years.
You buy cattle for a price. You feed them for 6 months, or 12 months, or 18 months. Then you sell them for a price. The problem is that in the 6-18 months, other people have decided that cattle are worth more or less than they where back when you bought. You can buy calves at $.95 a lb, add 600 lbs to them over summer, and end up selling them for $.65 a lb, getting less per animal than you actually bought them for - all depends on the cattle market cycles. You need to catch a cycle in the other direction every now & then to keep your head above water.
We are in a real tough time for livestock of all kinds. Be real careful. You can invest a lot, and lose a lot for several years be4 showing anything close to a profit with cattle - or any livestock.
Selling beef on the hoof directly to buyers, one or 1/2 half at a time, is where a small outfit like you are thinking of can make some real money. Most areas you can't sell butchered meat without SSS inspections; but hook yourself up with a local butchershop, sell live animals to buyers, deliver them to the butchershop, let the buyer set up their deal with the butchershop, and you can make some money.
The deal with that is it takes a lot of time to find buyers, you are dealing with one at a time so it takes time, time, time, and more time, and you need to be a good salesman & people person to find & keep customers.
Some parts of the country folks have moved in from other lands and goats are _very_ much in demand for these individual sales. You live near any communities like that - be othe only one with live goats for sale around such an area, keep good relations with that culture, and you got a mini gold mine.
Some sort of specialized nitche can really pay off for you.
So, forget your research on animals if you want to raise some.
Learn your local demands; figure out what kind of critter you love to work with even if you don't make a dime from them.
Combine those 2 with some good people skills and you can make some money on critters.
If you love raising & working with hogs, but hate dealing with a cow - doesn't matter what our research & studies show, you ain't never going to make it with cattle.
Boarding horses: Makes big money, makes big headaches from town people who love their critter more than their family and have unrealistic expectations of what things are worth. Oh boy do you need people skills to survive such a deal.
Remember - if farming were easy, everyone would be doing it!
There are 3 ways to make some money at farming.
1. Get really big - many many acres and play the farming game & make a couple dollars an acre most years. This would include renting the land out to someone big to use as part of their operation. This requires no time of yours, and kinda sorta pays the taxes and maybe the intrest on a loan. Maybe.
2. Find some niche in your area that people are willing to pay for - butcher animals, horse boarding, sod sales, etc. Treat it like a hobby & enjoy working with people & you will make some money to pay off the land & toys you use, but you won't get rich. You spend a little time, a little money on toys, and hope to break even while you enjoy working with people.
3. Find some real specialty nitche on just an acre or 2, and spend almost all your & your family's time on it - garden farming, sweetcorn patch, cut flowers, and so forth. You can make big bucks per acre, but really the land doesn't ccount - you are selling all the time you are investing, as these high-paying deals require _much_ time. Skimp on the time you spend on it, and the flowers or corn will grow up in weeds or go unpicked or full of worms & you got no income at all for a year. You are heavily invested with big bucks in either special seed, special equipment, or lots and lots of labor. Big payoff when it works, big hole when it fails. You only hear about the good years from others, not the big hole years.....
You are getting some suggestions from all 3 catagories.
Which one fits you?
In any case, farming is a long term investment - going to be 10-20 years before you see real income from your initial investments - land & toys - er implements cost a lot of money up front, you got to work them for 10-20 years before they get paid off & you see income you get to spend.
--->Paul