If you are looking to build a small herd for your enjoyment then go ahead, if you are looking to make money well, I am sure you know you are in the wrong bussiness,
Do it because you have a passion about it, not in hopes of making money. The horse bussiness is deffinately one of those scenarios where the good guy that does everything right and doesn't cut corners tends to finish last, but none the less, I believe in doing things right and being able to hold my head high in the end.
In my case, even holding myself to these standards, I have had people unable to grasp that I am willing to walk away from breeding just because I can not ensure where my foals will end up 1 year, 2 years, 3 years down the road.....
As much as I could handle putting my mares at risk and all the expenses, perils of ownership, breeding and foaling, I can't handle facing that one of my foals that may be todays treasure for someone, will end up being treated like tommorows trash.
So once again, only you can answer this....There are many unexpected bumps in the road that can occur,if something comes up and you feel as if you will want to change directions, will you be able to keep them, part with them, care for all of them the way the deserve to be cared for if you should decide not breed, will you try to offer this mare a forever home being that she is already a bit older or will you be trying to make your money on her foals and resell her when she has fulfilled her purpose (once again, even one or two nice foals may not offset te cost of vaccinations, feed hay, wormer, bedding, vet care, dental care, ferrier care for the time frame you keep the mare) , think of what your long term goals are for her.
Good Luck whatever you choose, if the decision is one of being a more of a passion rather than a bussiness, then go for it. There is nothing wrong with it being a bussiness, but in my eyes, that passion must exist in order to keep the horses best interest in mind.