Would a horse boarder/owner be interested in this?

I have a coming 4 year old paint mare that I am breaking and she is super lonely and kinda of depressed seeming. Our neighbor had horses at one time last summer but had to sell them and one was her buddy, since then all she does is mozey around and lay down.
I am looking for a broke horse that I can ride on the side maybe in local gymkhanas etc that would also be her buddy and maybe help me teach her some new things.
We cannot afford to buy a horse right now, so I was brainstorming and I want to know if this is something that people might be interested in doing. I have about a 2 acre pasture that she is in and I was thinking that someone could board their horse for free at my place (providing food and farrier etc still) but not have to pay monthly board, and I would feed, clean, take care of the horse but also get to ride it on the side. Kinda like a lease but the owner still rides him/her as well and takes care of food costs.
Is this something that a horseowner would look into since it would be much cheaper for them, but I would also have the companion for my mare and could ride the horse too?
They would be able to come over anytime and ride and check on the horse and before anything was made sure they could come check the property out etc.

I don't really know its a risky deal but the way things are going im sure someone maybe willing to do something like that I would just make sure all the I 's are dotted and t's crossed

Are you zoned for more than one horse?

Are you zoned to operate a business out of your home?

Insurance.

Liability.

Lots of variables to consider.

There are alot of free horses right now. My friend seams to have a new one each week, so I would just keep an eye out for a free horse, you can get good ones. Boarding is a real pain. People are a pain.

Offering board to someone (even free) can open up a can of worms you may not want to deal with. Legal issues, insurance, liability, etc.
An option is to talk to a rescue about fostering a horse for them. Rescues are overrun with horses needing places to stay until they find their adoptive homes. Some fosters will even pay for their feed and upkeep, you just have to provide them a place to stay.