I would say that without doubt an end of tenancy clean can, in a lot of cases be the worst cleans that you will ever do and if you can find work from other sources then go for that.
We provide a cleaning service for a few letting agencies/estate agents and generally you find that the property has been trashed, never seen a vacuum or polish and the toilets, bathrooms and kitchens can be a nightmare! I am not talking just about student properties, even some of the higher priced properties can be left in a right state.
Yes you will have to provide a carpet cleaning service or have a contact that can do this for you. You will also have to provide an oven cleaning service as well as a refuse/furniture disposal service, the last one we did needed a 4yd skip to get rid of the rubbish left inside!
You will also find that a lot of letting agencies want it done for next to nothing, make sure you agree the price with them after viewing and not before, also make sure you qualify the standards that will be achieved as they will also will want everything looking "as new" when this is often impossible to achieve.
Just a warning, not every property is grime heaven, but you will come across your share.
Good luck in your new venture!!!