Unless a registrar is holding a special common domains (com, .net, .org) generally will not be found cheaper then $6.75. Most hosts offering domains for free or at a reduced price if you host with them will not allow you to move the domain until your contract is fulfilled. So, unless you know the company and it's performance very well, you'd be better off paying the full registration cost through a reputable reseller and sign up for month-to-month hosting until you have confidence in your host.