You might be able to erect a shed style place for that, but that's minus insulation, electric, plumbing, finishes, furnishing etc etc etc.. $3k is fantasy land. 

The disadvantages in my opinion are the meeting and greeting and cleaning up after people. there is more management involved and what would happen to your profits if you hired the duty out? 

Your only option now is to come up with the money to buy the place or come clean and admit everything to the owner.

Quote from @Branden Rivero: The issue I see is the building is close to 100 years old and with a $500 hoa it's not an easy sale for an investor Yes, thats true however all expenses the past year increase insurance, sewer, trash, electric and cleaning service.

On one of my units the property has shared electric with another unit I own.

Regarding fire places, our friends that have older apartments with fire places are often filling the fireplace gap with electric LED "virtual fireplaces". 

After the cost segregation study was performed, this was the new asset allocation breakdown by useful life.Here are some examples of what types of assets are included in each of these asset classes.5 Year Useful LifeSpecialized equipmentCabinets and countersRefrigerators and microwavesSecurity alarm systems and telephone connectionsDecorative wall treatments, ceiling fans and flooring15 Year Useful LifeSidewalks, landscaping and asphalt pavingSignage and site lighting39 Year Useful LifeDoors, walls, roofing and windowsFlooring, drywall partitions and ceilingsEmergency lighting and restroom fixturesPlumbing, HVAC, and electrical distributionThe use of the accelerated depreciation strategy helps real estate investors to reduce the tax liability immediately which therefore increases their bottom line due to the offsetting of income.

I want to avoid holding costs with him holding onto it while we renovate, but how to I make this as clean as possible?

You have $606 after tax dollars to spend on the rest of life's expenses, including investing, buying flowers for your significant other, cell phone bill, water/electric/vehicle expense/food/childcare/hair cuts/vacation. 

But if you allow tenants to have pets it is not maintenance free and needs to be cleaned/sprayed down etc.