You have to self fund initially. There are some places that help, I think, like Cauldwell Trust etc, but still need to be running a programme first.
You can do it yourself, if you have time, and if your ds will permit (there is no way I could abbey with dd1 - her control issues re: me are too great)
Some places, like UKYAP run the whole thing for you, hence the cost. So they supply tutors, supervisors, the lot. Others, like Sean, you pay him to.comfort the day to train you/your tutors, and he oversees the direction of the programme. You find tutors.and employ them (can be hard to find) normally on a self employed basis.
The programme for your ds is highly individualized, based on a thorough assessment of his needs. We used the ABLLS guide when we started, you would be more likely to use VB-MAPP now I guess (newer guide) which tales you through step by tiny developmental step where your ds is and where he should be heading. Every area is or can be addressed, so you can target exactly what you need.