Regarding the oven cleaning association, as far as i am aware the only way one can be come a member of this is if you pay to do the training with a certain Southern based company who also happen to be behind the association, so not truly an independent association, maybe one day there will be one open to all.
Starting a non franchise operation is much cheaper with training and equipment costs will be around 3k.
You must be a hard working guy with all the other services you all ready do , so bear in mind it can take 2 hours + to do an average size oven.
Paul