
I have always, personally, preferred to buy/sell outright rather than get into a co-ownership. I had one breeder, not in the UK, who tried to persuade me to take 2 bitches, co-owning. I was suspicious because of 'history' with this person, but when it turned out I was going to do all the work, using her stud dogs, and she'd come in and walk off with pick of litters, I told her thanks, but NO THANKS. It depends on the individual situation and had I needed to get a couple of admittedly well-bred bitches to start my bloodline, I might have been persuaded. Lots of new people might have been 'flattered' to have been offered them! Having said that, some years later, I had a male who we'd kept back (from an all -male litter, unfortunately). By the time he was around 18 months, he started challenging his uncle resulting in some quite nasty fighting. Try as I did, I couldn't get him to settle down (he'd not been used, his uncle had) so in the end found him a super home. In his case I did co-own to begin with but once I got to know the new owner better, I signed him over to her totally, with no extra charge because I was happy to have found him a good home and have peace back with our small pack. In that case, I had a co-ownership contract, setting out exactly who paid for what.
If you do decide to co-own, just make absolutely sure you set everything down in writing - who pays for what, food, vet bills, any stud fees coming in (and I'd want some say in who gets to use him!). Just be aware, Contracts are often only as good as the paper they are written on (perhaps less!). Eg. I had a Contract with a fellow-breeder stating that I wanted one stud from the male they took (they had one of each). Fat lot of good that did as when he was around 2, before I could get to use him on one of my bitches, as planned, she'd sold both of them overseas. Too bad I hadn't put Not for Export on their registration papers .... at least that might have made the new breeder/owner think twice before taking them even if they still went overseas. Obviously once gone, I couldn't use him on my bitch.
If you get any hesitation about signing a Contract with this prospective co-owner, don't co-own. It would be better if you knew your co-owner really although even close-friendships don't always last! Whether or not you use a Solicitor doesn't really matter and may not be worth spending the money on to be honest.