What about a personal CRB check just for his own safety? That is only a thought.
I would not discriminate between disabled and able, elderly or young, if you start with a charge which must include the cost of any insurance and other overheads which you might have, and an hourly rate which will bring you the money for your needs, then that is the way to go. You are either going to make a go of it at that rate, or you are not. Do not do work for peanuts (voice of experience!) it just does not pay in the end.
Notices on shop notice-boards, a few flyers if you have time to put them through letter boxes, and a land line telephone number together with a mobile number - I think that shows that you do have a base from which you are working.
If you do a good job, people will not object to paying a little extra, and leave your card or flyer behind, word of mouth will be the recommendation that brings you the most work.