Opps! Might be too late spotting this one!
We have been cleaning the same 4 showhomes for almost 2 and a half years now. They are just selling them off now - only one left.
Furnished, 4 bed 3 floor = £50
Furnished, 3 bed 3 floor = £45
Unfurnished 4 bed 2 floor = £45
Unfurnished, 2 bed flat = £30
Marketing Suite = £20
(Yes you can charge extra for the marketing suite, even if it is in the showhome, because it will have the most traffic, Also toilets, sinks etc will be being used)
We did the initial build cleans, re-cleans, and sparkle cleans before starting the weekly showhome cleans. Then we got the rest of the contract for the site, 127 properties.
Our prices may be a little steep, but we had an inexperienced QS who suggested the prices for us. The contract was signed before anyone in accounts realised his error. But I would still never quote by the hour. You will be asking for problems from the sales staff later on if you don't spend the exact amount of time in each one, or if there is any kind of complaint about your standards. (and there probably will be - sales staff are notorious for being very picky!)
Also, you need to set up a rota of tasks. For example: Windows, inside and out, will need doing on a monthly basis. If they are furnished, you will need to wash things like ornaments and tableware fortnightly. Blinds will need a good clean at least every 2 months. You will also be expected to dismantle fancy light shades to remove dead flies (always worse in summer/autumn) Things like that.
Your weekly rota will just be the usual vacuuming, dusting and polishing, but remember to wipe inside cupboards and drawers and scrub away limescale from the standing water in the toilets. etc.
Hope this helps