50 years old isn't that old compared to much of what's out there.

However, two things that I observed - 1) the turnkey company I am working with has shared a proforma that has ~10% to 15% premium price compared to similar properties sold in the area. 2) they have a contract in place before the inspection and appraisal.

Compare that to some areas like driving park that went up by 35% i don't know why you'd invest in this area for long term hold.

Everything has been nicely redone, we only found one electrical outlet that didn’t work compared to the usual $15,000 worth of electrical I have done to most of my buildings.

You want to be able to compare several towns and locations and determine which has the greatest chance for success before you put your money down.  4.  

I still see $250K properties that have $3000 in taxes compared to other $250K properties that have $6000 in taxes.

That is how investors get ruined, happens in all walks of REI investing.Quit talking to and comparing yourself to your friends.

Compare your rental to others in the area and that will determine the appropriate rental rate. 

Single-Family Home with a Basement:Pros:Familiar single-family living with potential rental income.Can be a good starter home, quieter living if the basement is well-soundproofed.Potentially lower initial investment compared to a duplex (depending on renovations).Cons:Finding tenants might take longer, especially if the basement isn't a fully formed apartment.You'll be responsible for all maintenance and repairs for both units.Less separation between your living space and the rental unit.Multifamily Duplex:Pros:Clear separation between your living space and the rental unit.Potentially higher rental income with a full, separate unit.Faster tenant search as it's a more traditional rental format.Cons:Might be slightly more expensive upfront than a single-family home with a converted basement.Potential for noise complaints if the duplex isn't well-built.Dealing with potentially two sets of tenants (though vacancy rates are typically lower with duplexes).So, which one to buy first?

Read a couple articles comparing the two and I think you'll choose quartz.