I'm currently pregnant following DIY AI, and my partner and I found the donor on a co-parenting website, so it's definitely possible!
We found plenty of would-be donors who didn't want to co-parent and were happy with the kind of arrangement we were after.
It's maybe a little easier for us in that we're married and so my partner is automatically our baby's legal parent, but I know quite a few people for whom this is not the case who have nevertheless had babies this way. I think your best bet would be to draw up a sperm donor agreement that you both sign; they aren't technically legally binding, but should provide more than enough evidence to convince a court that you both went into the arrangement "eyes open". There's quite a good precedent for this, and lots of good info and templates for agreements etc online.
Aside from that, my advice would be to get them to have an STI check/fertility test/whatever makes you comfortable and show you the results (though I do know people who have actually gone to the clinic with the donor etc, just to be certain!).
Meet them in a public place as many times as you need to feel comfortable; if you get a bad feeling from them, don't be afraid to call it off. If they're legit, it shouldn't be a problem for them to meet up a few times. Don't give them any personal details until you're comfortable doing so etc etc. General "meeting strangers" stuff!
Be honest with what you want from this, and expect them to be the same—it should ring major alarm bells if they don't answer your questions directly or acknowledge your responses to their Qs.
We had quite a lot of message/email contact in the first instance, to weed out the creeps, but also (being cynical) to get it in writing that
they understood and were on board with what we were looking for. I found the creeps showed themselves very early on—we only ended up actually meeting one guy who turned out to be a wrong'un, and again, it was immediately obvious (was funny about STI check, wouldn't tell us his real name, was generally cagey).
Oh, and it's really good for making things less awkward if you discuss in advance exactly how things are going to go down on the day (eg no small talk, do the deed in the bathroom—I'll leave the sample pot out by the sink—then be on your way and we'll let you know in a couple of weeks). Definitely have someone else in the house/wherever you're doing it with you at least until the donor has gone too.
Agh, this is long! Hope it's of some use at least...
Good luck!