First you must find out if the zoning will even allow such a use. This will be the first hurdle,.
Next,. is writing a business plan. This will lay out in detail what your plans are and what the will cost as well as the investors and what percentage they own the business in.
Next talk to an accountant to make sure you numbers are realistic.
Assuming you have the money and or financing then create a LLC to protect you folks individually from liability. Then get a tax ID number for the LLC
Next proceed to renovate as needed and comply with any health department inspections required. You will have to comply with parking regulations and handicap spaces as well as fire codes. Be careful to document everything very carefully and hold on to every document.
If you have never hired anyone before take a course in business employment law(this can be a legal and costly mine field for newbies) and one in business management. Accounting is not an option so if you haven't taken classes in accounting you must. Your business must have accurate books or you will have problems with everything from taxes to your partners. Accounting is the water all business activity swims in.
Best wishes.