Tdk, may I suggest you take a look at the Racing Post online? Go to the BLOODSTOCK section at the top, click on SALES, then scroll down to TATTERSALLS and select 11-14 July 2006.
You will now see a range of fillies and mares who can be yours from as little as a couple of thousand to a Darley offering at £44,000. You can see the mares' breeding, their ages, and who's offering them for what. Those are typical options open to you.
The few golden rules I've picked up from Songsheet are to pick a mare that has WON and preferably one that has a bit of black type. You can pick up a beautifully-bred no-hoper, and you have to ask yourself why the animal was no good? Was she inherently unsound? Nuts? Stupid? It won't be the worst black mark in the world against her if she has never raced, but there needs to be a good reason as to why not. It could be that as a youngster, she whisked about in her paddock and damaged herself, which is fair enough. If it's because she refused to race three times, it isn't quite the same story.
You can also buy mares ready-made in foal. Songsheet and I bought REACH THE WIND in foal to AGNES WORLD, for example, as 'Doris' as RTW is known at home, was knocking on and her stud wanted room for younger mares. She had one further foal and we've now retired her, being 'out of' her money-wise through the sale of the first foal. The current yearling is probably being offered later this year (by CARNIVAL DANCER - waaaay cheaper than Aggie!). So, you can, as an alternative to the long haul, pick up a shorter-term breeding prospect with an excellent sire for much less than a younger mare with many years of breeding ahead of her, as an example for you.
I know nothing about breeding - the expert is Songsheet. If you're not an expert and au fait off the top of your head with who's a bleeder, who gets as many cripples as sound foals, etc., then may I very strongly suggest you attach yourself to someone who knows what they're doing! You could select and buy yourself a nice enough mare (and I assume you've got somewhere suitable to keep her), but find that the 'lovely' stallion you've selected on the grounds that he's won a lot (I offer TOMBA as an example) just doesn't get that many winners, and few people but his owner uses him!
The topic on failing new stallions demonstrates that a fabulous track record doesn't always translate to a fabulous line of winners. I wouldn't breed to a sire who'd been retired because of unsoundness, either. There are enough things that can go disastrously awry with your foal without helping it on its way with wonky legs!