Difficult one. You don't know how often lets would be. Could be 1 night each for 20 let's or 10 let's for 3 nights while 5 could be 2 nights etc so you have to be on call 7 days a week and get them all ready before check in time of say 11 am after check out is 10 am. Then there is the change of linen and towels. Who provides that and where is it kept. So price on time taken. I had enquiry for 20 but turned it down. I look after 1 that is very close, 2 bed, lounge, kitchen , bathroom. Takes 4 hrs with the laundry. Charge accordingly to your rate per hour.