Both are legal here but in our lease, it states that its a non-smoking/vaping/drug-use building, which they signed.

As long as he/she is not using the treadmill in an illegal time based on your city/county regulation.

The thing that really hampers development, especially the commercial/industrial sectors is the large amount of impervious cover (concrete) and the Little Cypress Creek Frontier Mitigation Program with how HCFCD has set up detention regulations.

FL has too much this type of licensed 'professionals', cheap cookers, but the DBPR is very loose on regulation.

whats the best way of finding specific laws & regulations in my area with having to search for it throw my cities websites? 

Make sure it is a mature market (well established) that has friendly regulations where the municipality has already found a way to monetize through tax revenue.

One of the lenders I talked to this last week stated that with the new COVID regulations they wouldn’t be able to count my rent as income due to it not being signed to a year contract.We would like to buy a second property, owner-occupy it, and rent out the current unit we live in.

It would violate the State law for an unlicensed person to get a commission in the brokering of a real estate transaction --- its a regulated business. 

Costa-Hawkins forbid vacancy control, wherein rent is regulated when there's a vacancy.

That way you know the laws and regulations for the state you're in.5) Constantly educate yourself.