I am guessing that you are going to have to do a lot of work to create something in Access that is better than what is already out there. I regret to admit that a lot of people want a quick fix to their problems so they are very apt to buy off-the-shelf junk that is pretty looking, but does not do the job like intended. I'm guessing you are going to have to do a lot of talking and convincing of others to sell your applications.
I also think that access apps need to be very sophisticated in order to sell themselves, at the MINIMUM. I don't doubt that selling software is possible, but it really has to WOW the buyer I would think. I'm not trying to discourage anything, or anybody, but figuring out what is in demand might be the biggest challenge in itself.