Heather. Taking a horse on, as a purchase or as a loan is a 24hr /7 day a week committment. It will one way or another cost you about £3000 per annum - unless you don't have to pay livery fees.
Timewise - once a day at least, every day of the year - unless you organise someone else to do it for you.
So lifetime committment + cost + daily committment
DO YOU REALLY WANT A HORSE?
The taking on of a loaned horse is relatively speaking no different from buying one in many cases - except of course, in theory you can send a loan horse back - maybe.
You must make out a written agreement with the lender and in the agreement you must spell out who is responsible for what. That is an issue which in itself calls for a lot of thought.
The matter of insurance must be thought out - who pays?
In my mind, it is imperative to be sure as to why the lender wants to pass the horse on. The real reason might well be hidden. But you must ask bluntly - why are you giving up the horse?
and finally - the horse.
No considerations must override the basic requirement. The horse must suit your purposes. If you don't get on with the horse then no acceptable agreement is worthwhile. You must like the horse and the horse must like you - that's an imperative.
Your doubts are a factor to take on board. If you are nervous now, what lies down the road?
My advice . Well before you make a decision, visit all of the local livery yards and ask about as to whether there is an owner who wants another rider. I'll be surprised if you have to look far.
But again - if you decide to go in with another owner, then sort out the basis of your agreement before you start. And write that agreement down.
Personally I can just about share my horse with my wife - I can't see my sharing Delta with a stranger.
You are right to think twice - it is a big decision and one to be taken only after careful unrushed consideration.