There is a guy local to me who does this sort of thing. He handles the setup, maintenance, and teardowns of aquariums in the area. He does not have a storefront, but it heavily tied into a LFS which brings him many new customers while he directs people to them for equipment... He works at the LFS while doing the consulting part time as a side business. However I feel that it could turn into a full time business if he wanted to to, but with a full time business you need to assume the failure risk...
I would suggest getting in with an LFS that would like to offer maintenance services but doesn't have the means to do that. It would allow them to advertise they have maintenance services available which would increase sales and you would charge the labor side of things for the setup. It could benefit the both of you.
What I know from personal experience and dealing with a small time consulting effort of my own is you will find people who will use the service for different reasons. Sometimes it is due to being a price leader, sometimes they have an emergency issue and need help ASAP, sometimes they are too rich to do that kind of work, but sometimes they are just lazy too. Here are some questions to ask yourself though:
1. Are there other companies you would be in direct competition with in your area?
2. Do you have the knowledge to prove to your customers or future customers that you are a better solution than your competitors?
3. Do you have the means to haul heavy equipment and deal with the setup of multiple different systems?
4. Have you figured out yet what your competitive edge will be against your competition to drive customers to chose you over the others in the area?
5. Is there room in the market or demand that is not being met, that would support an additional consulting business to form?