I've stayed in the Bank St Lodge a few times Mole. They have singles and doubles, as well as 4 bed rooms. Always been fine. Central location. There are a few other bunkhouses/hostels. The nearest campsite is a few miles away in Glen Nevis.
I've also stayed in this one. Another central location. I like to be near the pubs!
Stayed their several times, it has a wet room and you can sit in front of the fire and drink till you drop after a good day in the hills.
There is a camp site at the base of the tourst path going up Ben Nevis, though you can camp anywhere on the Nevis route once on the path and across the river, if you want it really cheap!
we stayed HERE in July and was really good. Clean tidy quiet. hot showers, food if you want it. A great place to explore ben nevis and the surrounding area. The YOUTH HOSTEL is just down the same road. I suppose it depends how cheap you want it.
Calluna Self Catering is an excellent place to stay. It is run by Alan Kimber, a very well known mountain guide - there's even a bouldering wall on-site!