Parking. And location. Good luck.

Zoning will have allow that 'use' in the zone (along with other concerns), Building Department may require certain wall construction between certain uses (along with other concerns), There may be a type of Home Owner Association that may have concerns, and anybody else that wants to get their grubby little hands in your business.

Houston has no zoning.

You will also need to contact insurance companies as the house won't be used as a residential primary address. So you will have to see about insuring not just you business but the building and property itself. You will most likely need a lot of different inspections throughout the process, so I would check with you city building department about the codes and steps for renovating.

ALL of the renovation would have to be permitted. In most jurisdictions you would need to submit architectural, plumbing, mechanical and electrical drawings for approval.. There are a number of codes that you would need to comply with - International Building Code, Fuel gas code, National Electric Code, etc. And, as you said, the building would have to be handicap accessible and you will be required to provide accessible bathrooms with the needed number of fixtures. The work would need to be done by a licensed contractor. You have a lot of hoops to jump thru in order to accomplish your project. It won't be a quick process. So, it's good that you are starting now.

My brother-in-law wants to turn his house into a saloon, and is making great headway.

You might be better off buying a building already zoned appropriately and remodeling it to look like a cute little house.

If you haven't started looking for a realtor, start now. Some agents are more into commercial, some more residential. You are going to want to use either an agency or agent that can dip into both sides. If you have a local small business association/counciling/ect entity, look them up. They often help people with finding locations, and navigating the legal and municipal tapes. Some of these groups are free advice, but to my understanding some are memberships. I don't know what kinds you have by you. Check out areas you think you might want to set up shop in too. Start keeping tabs on those areas.

Check with your current business insurance. Ask them about insurance needs for your plans. Then ask a couple more agencies to compare with. Right now you are a renter, but your business coverage will need to also include the building, property, and maybe some extra for the parking on the property if you have it.

Depending on where you are, garbage service might be a consideration. If as a renter it is provided by the landlord, you would need to find out how to have garbage service at the new business.