Wall and floors will likely not be level there are usually multiple additions from different decades and building codes, if any.

The code inspectors have files on the property but they're all marked closed.  

I would check with local city codes and make sure what licensing is required, you are essentially operating a hotel model.

@Sean Peters I think your attorney friend is your best resource in this, but if your tenant has an option to renew that's a part of his lease, I think you have no choice but to honor it - unless you evict for breach of contract.I suspect that if you do not evict and then raised the rent beyond what the contract allowed, a court would find you in breach of contract.If you do evict, be sure that you have your documentation complete right down to the letter.  

Before embarking on a career in real estate, Derrick served his country honorably for nine years in the United States Navy supervising young aviation electronics technicians. 

I also try to "break" the product before it ships.I work closely with the developers to make sure the code they write does not negatively affect our product in anyway. 

They should be vented to the exterior otherwise they only serve the purpose of being a coarse particulate filter and do little for the air quality within the premises.In the IBC/IRC and building code in many, if not most, jurisdictions range hoods must be vented to the outdoors.

Best way is to obtain authorizations for release of credit, tax returns, assets and liabilities, then send copies or get several originals to use, mail them  and obtain information directly from the source, this cuts out the chance of fraudulent statements.You also need to underwrite the type of business, what hazards are present, toxics, fire, insurance coverage, competition with other tenants, traffic counts, environmental laws applicable to them as well as your infrastructure being sufficient for tha use.....electrical, plumbing, traps, fire codes, etc. 

The term "real estate professional" is a specific nomenclature in the Tax code that has specific costs and benefits which (I believe) are different than what you're talking about.

You’ll need to check local codes but if it’s zoned duplex, but currently the use is single family, you should technically be able to convert it if you bring it up to code (IRC - the version varies by jurisdiction) which requires attached two unit dwellings to be separated by 1 hour fire separation.