We do not do many Tenancy Cleans, but the ones we do seem to be last minute, On this job you will be better off not charging by the hour, but do calculate the hours for your own calcualtions ie: make sure you see the property first and estimate how long it will take- calculate what it is going to cost for the labour - add your margin, that will give you a figure that you are willing to do it for.
Also factor in the day / time the client wants you to do it - ie : evening / weekend ect.... as this will effect your labour cost, and you will get away with more...
Hope this helps...
Cherie