instant and free.

Instant increase?

Instant gratification v. delayed gratification.

If the appraisal comes in higher, the difference between the value and the purchase price is instant equity.

To find something in your price range with instant equity is pretty much not gonna happen.  

It sends you directly to DBPR website to start a "dwelling" application which a single family home falls under. 

The dwelling must be brought up to legal permitted habitable standard, then you may evict. 

.: "A taxpayer may claim a credit of 30% of qualified expenditures for a system that serves a dwelling unit located in the United States that is owned and used as a residence by the taxpayer."

(A) A landlord who is a party to a rental agreement shall do all of the following:(1) Comply with the requirements of all applicable building, housing, health, and safety codes that materially affect health and safety;(2) Make all repairs and do whatever is reasonably necessary to put and keep the premises in a fit and habitable condition;(3) Keep all common areas of the premises in a safe and sanitary condition;(4) Maintain in good and safe working order and condition all electrical, plumbing, sanitary, heating, ventilating, and air conditioning fixtures and appliances, and elevators, supplied or required to be supplied by the landlord;(5) When the landlord is a party to any rental agreements that cover four or more dwelling units in the same structure, provide and maintain appropriate receptacles for the removal of ashes, garbage, rubbish, and other waste incidental to the occupancy of a dwelling unit, and arrange for their removal;(6) Supply running water, reasonable amounts of hot water, and reasonable heat at all times, except where the building that includes the dwelling unit is not required by law to be equipped for that purpose, or the dwelling unit is so constructed that heat or hot water is generated by an installation within the exclusive control of the tenant and supplied by a direct public utility connection;(7) Not abuse the right of access conferred by division (B) of section 5321.05 of the Revised Code;(8) Except in the case of emergency or if it is impracticable to do so, give the tenant reasonable notice of the landlord's intent to enter and enter only at reasonable times.

You would need to check with your local city permitting department and if your property is in a subdivision with HOA or deed restrictions you will want to verify you can build a second dwelling on the same lot.