Get yourself onto the facebook home ed page. There's a map there of local home ed groups, which might help you begin to get in touch with other home educators in your area.
If you haven't already joined your local library, that needs to be top of your list, so that you can regularly go and get books out.
Start looking for the best deals on annual passes at interesting places near you - you probably can't afford more than one or two for a year, but it might well be worth doing just that one or two and then squeeze every ounce of value out of them, and then do something else next year.
You are really going to need some real life support. If you can find local home edders, that might help provide that support (although you might be a bit isolated geographically). If there really aren't many/any near you, then get ideas from here, facebook, blogs etc etc about the ways you can educate your son- there are all sorts of different flavours and you need to find what suits you both.
Keep up friendships with his school friends as much as you can, especially because there probably aren't many HEers in your area.
You'll need to think a bit longer term about what happens with your financial situation as he gets older (I think you lose benefits at some stage, don't you?). Think about the sort of work you can get that you can work around with child care (I know people who teach forest school, and their children go along too, that sort of thing).
And please bear in mind that, even if your own spelling and grammar and so on are not as splendid as the mumsnet posters might like (a) this is a great opportunity for YOU to learn about grammar and spelling side by side with your son and (b) Paula Rothermel's PhD at the university of Durham showed that the educational outcomes for HE children from poorly educated backgrounds were greatly enhanced by them being HE, over what they would have been had the children been left in school. You may well be doing your child the greatest educational favour of his life.