Going for deal #2! Question bout partnering with parents! HELP!

Hi everyone! We are really excited our 1st investment property, a vacation rental in Ocean City, Maryland, is going so well this year we will have a chunk of change to put into a second investment property this fall/winter! Depending on the deal we may need partner with my parents who are very interested since we have done so well with the first one. Im trying to figure out, what would be the best loan to get. A conventional second home mortgage (I guess primarily under my parents name since they dont have a second home like we do) or a realestate investment loan under both our names? There is so many ways to do this and of course I want the lowest interest rate and it would be great if we didnt have to put down 20%. Any ideas??!! Thanks!