@Tom Dever I would absolutely do it again, and I think I'd stick with the single-family house. Our house was on almost an acre on a corner lot and was pretty wooded, so people liked the privacy and the quiet. We also allowed dogs - and brought our own - which I'm not sure would be the case in a condo.
Spring was certainly a dead time, but that's when we'd head up to check on the house, relax a little ourselves, and see what updates and repairs were needed. I didn't mind it, to be truthful, because it gave us a chance to enjoy the house ourselves and to catch a breather before things got humming again. Summer was quite popular. There's a ton to do up there from June-August between the mountains, lakes, outlets, etc. and we'd get hikers, bikers, rock climbers, and the occasional fishermen. We found that summer was when families would come up to visit Story Land and other attractions, while winter brought the skiers. Fall of course was leaf-peeping.
So the dead zones were April and May, along with late October through about mid-December, though we did always have requests for the long Thanksgiving weekend. Having said that, I think if I was a better marketer I could have run some specials and filled in some of those quiet times. If not, I still believe there's plenty of cash flow to be had between the peak winter, summer and fall dates. If you buy it right, of course. :)