Here's what I don't mind sharing about what I do and know of :)
My dream was to train horses and do train and resell projects. I absoloutly LOVE and ADORE training. But, there isn't a lot of money in it, unless you are a top of the line trainer. So my training, as hard of a decision as it was for me, has become my spare time/hobby - that I make time for, and it's great for bonus money being made on the side, but no way to make a living off of. You have to factor in feed and time mainly. You have to think of the train and re sell projects as a job (which is hard for me since I always end up falling for them) but you need to get them in and out to make the highest revenue, but also do a quality job and leave no holes in your training - the latter is where you loose money. The longer you have the horse, the more money goes into it.
Doing your own breeding - there isn't a whole heck of a lot of money to be made there either. You put all your money into the stud for his training, then your broodies feed, AI, ultrasound, etc. Then the baby care when they get here, plus all the work and feeding for the outside mares. Even if you sell foals in-utero, there isn't a whole heck of a lot to be made in my experience. If you're lucky, your stud will bring in a little money, to kind of cover his costs.
For the rest I'm not so experienced in, I had thought about boarding for awhile, but didn't want the drama, with some of the barns I've ridden at around my area - there's just WAY to much horse drama in my town.
I've settled with the job I have now, because I can afford my horse habit off my wage. It was a hard pill to swallow at first, but you have to do whats right for your situation. Off my wage alone, I can afford my horses, just bought a new trailer, bills and my fiance' helps with the rest (as he should :)). You need to do the soul searching and figure out what you want and what your connections are in the horse world. And just because you have connections doesn't mean it'll be easy either. I worked with a well known trainer around here, and he doens't make a whole lot after everything, and I sure don't either.
Find where your heart belongs, and you'll figure out the right choice :)