So far we have painted the common areas and the exterior of the building.

In future if I decided to build and convert both lots to one apartment building should I convert 2 parcels to 1 parcel?

Depending on your income You get to take depreciation off your regular income (usually up to $25k) of 3.6% per year of the building’s value.Many of your everyday expense can be deducted from your income as business expenses. 

When speaking to the owner (building rapport), your main goal is to figure out which of these main 3 is most important to them.

My question is, can I use one of the separate parcels as collateral for a construction loan to build a multifamily on it (of course adhering to zoning regulations)?

I've recently taken on a project to build three SFRs on adjacent tracts of land.

Smaller office or shop buildings might bring in more money but need you to know more about running them.

Get rid of debt, build a budget, and save.

Get rid of debt, build a budget, and save.

Definitely a smart idea to do a few fix and flips to build your cash up first!