The two existing LTR units (on my family’s property) were built 5–8 years ago at a cost of about $80,000 per unit, so I’m estimating a 20% increase in costs for the new builds.My plan is to use the equity in the land as the down payment for the construction loan, which I expect will make closing costs the primary upfront expense.

This way the lender is covered and only lending on the value that is legally zoned and compliant (in case the city took action against the non-conforming unit).

Now let's say I find a triplex that covers the 1% rule but combined cash flow from all 3 doors is roughly $150-$200 or would you want to keep it at $150-$200 cash flow per door with the 1% rule applying? 

I'll subto his existing mortgage and pay off the 120k.

The biggest thing with this is if something major happens are you legally covered if the unit is illegally rented. 

How will the existing income from the property influence the amount I can borrow? 

Just like in Southern Italy, where houses are sold for as little as one euro, similar initiatives exist in Spain to attract people to repopulate villages and revitalize these areas." the one part I'd disagree with is "many".So why was I shocked then?

Only in community property states, can an LLC with only husband and wife as members elect to treat their LLC as a disregarded entity, which means all LLC income and expenses are reported on either Schedule C or Schedule E (as appropriate) as if the LLC did not exist.

From what you wrote it sounds like the rental you own is your sole, pre-marital property.

Even if you manage to find an office with an existing tenant, their lease could be approaching expiration, and without plans to renew, it can take an incredibly long time to secure a new tenant for the space.