Lake Leschenaultia is near Chidlow WA, only 50kms from Perth.  Their campsites cater for tents, camper trailers or campervans (but no caravans or motorhomes), see their link prices etc on this link;

http://www.mundaring.wa.gov.au/YourCommunity/RecreationAndLeisure/Pages/LakeLeschenaultia.aspx 

They do allow a caravan/motorhome/bus etc in a special site free if you volunteer to be a Caretaker there for a short period up to 3 months, free site with water/sullage and power in exchange for caretaking at night until dawn, sleeping shift from midnight on call only.   There are no other duties eg; cleaning/gardening etc. The Lake has hot and cold showers campers kitchen,free washing machine/dryer and mains water.

If you are interested in doing a short stint there (unpaid, free use of site and facilities only) it is an ideal position for a single or couple to have a nice break in the Hills area, days are free to do/go wherever, including having fun in the Lake & surrounds.  Contact the number or email shown on the link for the Lake Rangers (not the Cafe) and ask to speak to Andrew Lee, the Manager. 

I should add (too late for edit on previous post) that I have just completed almost 8 weeks there as a Caretaker and it was a great holiday and you get to meet some very interesting people