I'm going to split the cost between myself and a friend, but I'm not sure if Myqth will be good for us because we both have more then one web site. And if I get a domain name, things might get mixed up. What do you advise?

I'm not sure if they allow more than one domain per account (something to ask them about), but assuming they do, what exactly is your question?

should i go with them?

i'll pay monthly, never yearly, heck its just 5 bucks per month, y don't u just give them a shot