OK, OP, all of us were new once and most have made expensive mistakes that could have been avoided if we only knew how much we did NOT know. So this is not spoken from a superior position but from actual bad, expensive, physically painful and confidence busting mistakes. Add misplaced trust in the wrong people for the wrong reasons to the blunder list.
Try doing this, you should have already but guessing you have not. Make a list of routine monthly horse expenses you will be responsible for whether you ride or not and price it. Assume it is stall board. And be aware this is what you’ll pay to full lease, not just buy, part leases vary but will be based a percentage of these costs.
Monthly board What does that include, specifically?
How much hay fed how often each day?
Grain?
Do they feed at least 2xday 7 days a week?
Auto waterers or buckets, if buckets how often checked and refilled?
Stall cleaning and bedding?
Do they turn out and bring in?
Lights in the barn? (Don’t laugh, its not a given)
Farrier services, assume every 6-8 weeks. OTTBs can need special help there.
How much for the farm call?
How much for a trim?
How much for trim+Steel shoes? Aluminum shoes?
How much for trim and reset (steel only)
How much for full pads, rim pads, pour ins? Wedge shoes? Bar shoes?
Routine vet. Twice a year. If you are lucky.
How much for farm call?
How much for required Coggins?
How much for spring and fall shots recommended in your area, possibly required by barn?
What worming protocol will you follow and what will that cost?
These are the minimums for most horses wherever and however they live.
Of course, if you buy it, you will need a halter, couple of lead ropes ( they walk off), grooming tools and maybe a blanket or sheet. Price those in.
Of course saddle if you don’t have one or it does not fit, new horses never like or fit the bits and bridle we already have, thats a given. Price that out.
Just by what you have shared with us, this trainer does not have a secure business and could fold at any time. Then what? Don’t get in with her too deep or depend in her for underpriced services or provide anything to you. She goes poof, you are screwed.
Oh…note training services and lessons are not included in above costs…you need to price that out too understanding those rates will increase if she goes bust.
Getting with a better barn and program will help you educate yourself on the true costs involved before taking them on rather then find out the hard way…as many of us did and are trying to help you avoid.