Can you confirm your location. From your name, I am assuming for this post that you are in Cwmbran, Wales and therefore regulated by CSIW.
For childcare vouchers, Childcarers Guide may help explain a bit. I have yet to accept vouchers, though it is due to happen at some point soon. From what I hear from other providers, some vouchers are good, others not so good - this is in terms of their quickness in paying out to the provider.
With regard to having your DH working with you:
Look at Standard 13
Adult Child Ratios
The easier thing to do regarding DH is to make him your assistant - it's less paperwork and will let you try it out for a while to see how it goes.
With an assistant you may or may not be able to take additional children. Max number you can care for is 6, which includes your own children. Having an assistant does not increase this number, but if you are not already allocated your maximum of 6, you may find having an assistant puts you up to the maximum - subject to there being sufficient house space.
If you have a lot of space and once DH has settled into working with children on a day-to-day basis, then you can see if he will register as a childminder in his own right. In theory this could then permit you to care for up to 12 children (including your own), subject to space and I suspect other factors.
Standard 19.5 gives the space requirements for children in each age range. 2.5sq metres for children aged 2-7 years. To measure space, create a 1m x 1m square using newspaper, and see how many times that will fit into the rooms you intend to use for childminding.
Hope thats of some help.