Click on the link at the top of this page for book ski apartments in Bansko. They have a selection of apartments there. They will transport you to and from the airport. You can rent a car via rentacarbulgaria.com and collect it at Sophia airport as we did in the autumn.
Thanks. I heard that the airport rentcars close early, as we land at 01:00 am...
All the appartments I found are for families. We are 8 persons, 4 couples. I didnt even find one big apartment with 2 separate bedrooms, so we can take two of those.