Most trainers are averaging £1200-£1400 per month per horse, Helen. Then there are all of YOUR costs, like getting yourself to the courses it runs at (if and when!), any overnight stay needed and a meal.
This is why it makes such good sense to join a syndicate put up by a trainer or an owner, and there are plenty, and most of them are very well run. Even with a HUGE racing club like Wavertree (of WAVERTREE WARRIOR fame), or Elite, you get the chance to own a nice performer who will give you a good day's fun for relatively little. Most clubs just get you to pay a joining fee, syndicates usually ask you to buy a percentage of the horse on offer, then an appropriate portion of the training fees each month. The bigger the syndicate, the less you should have to pay out.
If you ever feel you'd like to be in the owning game, check out any trainer/s near where you live (because you'll want to visit without making a 500-mile round trip) and see what they offer in the way of their own syndicated horse. There are a surprising number of trainers who offer such opportunities, and then you can check out the sort of success they have on the RP by searching for the horse's name and seeing what it's done.