I have great credit and I am looking into 0% first year credit cards to utilize. 

In many cities, I am seeing significant quantity of unit construction starting too take place and housing prices rising extensively.

@David Pham Terrell Johnson I'm the owner/operator at dcm contracting service I'm licensed and insured my prices are very competitive and I have a very extensive renovation portfolio.

What will your monthly expenses be for:Any utilities you have to payYour maintenance costsYour vacancy costsYour CAPEX costsYour property management costsAny other costs I may have missedWhat net return are you looking to make on this property?

You should be able to ask the owner about the extra costs (utilities, HOAs, insurance, etc.). 

Am I going to need some kind of extension for the toilet due to the increase in height?

Laundry leased assets in closet nets 220/yr.Individually metered electric (heaters), no HVAC (standard for that area and age unit), but building utilities run 5k/yr - probably business utilities not being paid - unsure.

I doubt it allows for 2 units (it’s probably SFH.) assuming that, you can’t make it 2 legal units (adding an ADU is different, as I don’t think you’re allowed to take space from the main house for the ADU- it’s usually added sq footage.) and even if it allows for 2 legal units you may have to add a second parking spot, separate utility services (read: expensive and a PITA to install.)So the simple plan is to basically do the minimum work needed, as you describe, without permits just to separate the 2 living spaces out.

Ideally you would have had a clause in your contract that allowed or did not allow tenant placement or lease extensions during the term of the contract.

You may get better tenant retention if: (1) the tenants are paying utilities; and (2) the existing windows are so old that it barely insulates.