Hi Saffron and welcome
There are threads here with advice on working out your fees, but there isn't anywhere which says 'You Should Charge X Amount' because there is no right or wrong answer and there are so many factors to take into account. We have ladies on this board who charge everything from under ?100 to over ?400 per hour, and all of them are completely right to do so provided that their rates are getting them the amount of work they want - I would think most of us are in the 'average' ?100 - ?150 per hour bracket but it depends where you are based too, as some towns and cities are notoriously cheap.
The usual advice and still the best way is get Googling and look through sites like Adultwork to find out what other similar ladies in your area are charging and find the sort of level you think you would be happy with earning. Decide how busy you want to be - lower rates mean you'll have to see more clients to make the same money but it won't be so much of a disaster if one or two cancel, and higher rates obviously mean less work for the same money and therefore more free time to do other things if you're trying to fit the job around other work or studying. The bottom line is nobody can tell you how to work - all we can do is describe our own experiences and make suggestions.
Don't worry about your house - provided it's clean, comfortable and safe, clients aren't interested and more than likely won't even notice. When I moved into my apartment it was practically derelict and even though I got the bedroom done straight away I hated herding clients through the rest but it really doesn't matter. There is a lot of information here about both incalls and outcalls as well as working from home.
And yes, 99.99% of the time it does all come down to sex. We do get dinner date bookings and suchlike, but they tend to be at a fixed rate which includes something like two hours 'social' (eg dinner) and two hours 'private' (eg shagging) time. Most bookings comprise the second without the first - the first without the second would be virtually unknown - I've done one 'social only' booking in nine years, and that was a client I'd seen before for a normal booking who had injured himself in an accident but wanted to see me when I was back in his town, so we went out for dinner (and I wouldn't have agreed to it unless I'd seen him before).
If you want to do half hours, do them (I don't, but lots of ladies do). If you want to do overnights do them, but be warned, they're stressful, exhausting and nowhere near as lucrative as they might look on the surface. The best advice I've found for starting off is to keep it simple - if nothing else, there's less to remember.