Rich,
First of all unless you can get some pretty expensive horses you are going to go in the hole raising horses. There are too many "mutt" horse out there now. You can go to the horse sales and buy good bred horses all day long for less than a $1000. Good older trained ones for $1500-2500. Now just to get that foal on the ground is going to cost you a minimum of $1000, so if you sell for $1000, which you won't, the day the foal is born you break even for 11 months of work taking care of the mare. Now if something goes wrong, and it will at some point you are going to have some expensive vet bills. The $1000 comes from the cost of keeping a mare for a year, vet checks, stud fees- not a very good stud at that, etc. Anyway I've done the math every year for too many years to count and it's always the same. Unless you have a very good foal you aren't going to get a $1000 from a low grade mare and stud. Plus there are too many good horses out there to add more "mutts" to the list. Now unless you know how to train horses add about $500 a month to get one broke and ready to sell. To get one trained really well you are looking at at at least 6 months and $2-3k. If you can train one yourself then you only have the about $50-100 a month it will cost you to keep a horse. ANYWAY what I'm trying to say is that unless you have high dollar horses you aren't going to make any money on them and will probably lose big time. And you only get one foal a year. You would be much better off to spend $1500 on some good bred dogs and sell puppies. You would make 50 times the money you would selling horses. I don't even consider buying a mare unless I know that I can sell her baby for at least $3-5k without training. My stud horse was $25,000 and that's cheap for a good one. Unless you can spend some big time money then it's not worth it to try and make money at. Most anyone who's honest about it will tell you the same thing.
Now as far as what Ron said about boarding there you could make a little money, but the work you'd have to do would not be worth it in my opinion, plus you have people with access to your place at all times. To full board a horse you are looking at between $100-500 depending on where your area is. You have guaranteed income there but it's alot to keep up with the horses. If someone is paying you to keep their horse they usually expect alot.
The draft horse and miniature market is the same. No depend for low quality horses and not worth your time to breed them. You have to spend alot to get started and have something that people will pay for.
If I was you as far as horses for money don't even think about it. It just doesn't pay.
As far as other animals that you can make money on without there ever being a consequence that's a tough one. Most animals are raised for either their pelt, their meat, etc. Anything that you could make money on is going to end up in some kind of product. You could raise chickens, but again alot of work and eventually they have to be culled when they start laying and well what else do you do wiht a chicken that doesn't lay eggs? What about raising a vegetable garden? Farmer's markets are huge around here. The small vegetable farmers bring their vegetables into parking lots, etc. on the weekends or specific days of the week and sell them. Nice profit there. Don't even think about wool though. There hasn't been any money in wool for 20 years and not looking good in the future. The problem with animals, unless you find a niche like dogs, is that anything that has some real value the corporations have all made it into a science and for you and me to try and raise anything and sell you operate on a thin, if any, profit margin.
Sorry I can't be of more help, but horses aren't the way to go with a money maker.