From retreat experience: All on one level . . . Plenty of room between tables . . . Comfy beds . . .theme ie: bears, woodsy, ducks, etc. . . Delicious meals . . . Plenty of bathrooms . . . Location, location, location . . . Several ironing and cutting stations . . .
If the guests are coming from the city they will want peace and quiet.
Retreats are fun usually but we've been where the employees said they almost had knockdown fights between some of the campers.
Retreats are a HUGE amount of work.
Not to be negative, just double or triple the amount of work you will think it will take. Plus don't forget about insurance, zoning, taxes, etc etc.