Bookrentcar.com is close but not quite. Bookrentalcar.com could be a good one but the plural version Bookrentalcars.com would be even better. Namehealthy.com is kinda catchy, stronger alternative that comes to my mind is Namehappy.com. Unfortunately, I can't think of a potential buyer for neither of them. Loanlaundry.com sounds too much like something illegal. Myhyfy.com is the only real brandable among your names because to me it's just a freestyle version of 'myhifi'. Maybe Mywyfy.com is better but still not worth registering.
All in all, always try to think of a potential buyer for your domain. Did you register the domains yourself? If yes, make sure to check a domain's history beforehand next time. And hey, don't give up. No one was born as a first class domainer.
PS: Guidemedoctor.com made me giggle a bit. Potential name for an internet cult. Please don't take it personally.
Best of luck
Mike