@George Baal I would recommend taking out the HELOC to start but given the high variable interest rate, I would then consolidate that debt into a better financial vehicle.

There is a 10% variable on rents, meaning we can get 10% more than the market average if we are in the right neighborhood and have the nicest finishes.

@Jonathan Moody Good information but I'd like to add some additional points (note that your mileage will vary due to numerous variables). 

So I know this doesn't help, but there are many variables that affect commercial rates at any point in the market cycle: i.e.

Right now I am liking pickle-ball courts as it is the fastest growing sport in the US.It is very, very important to understand all the revenue and expense variables and then to have peers cross-check your analysis.

@Samuel Metcalf- thanks   1) I would recomend getting a HELOC in place on your primary residence duplex  for  as much as  possible...this should be available for  free or a low  cost and the rate will be variable in the  8-11%  range ...prime rate +  margin of  1-3% ) ...the min payment is in interest only payment on outstanding balance   2)  use the heloc for the  remodeling  costs ...pay it down as  agressively as you can   3) on the  purchase of the investmenet  1 unit -  you are  allowed to put as little as 15%  of the price for your down payment ...the pricing you get for the loan will improve  as your down payment  grows so you might look at  75% /  80%  and  85%  ltv  options 

Probably too many variables to make a blanket statement but might as well ask...

There's a lot of variables at play.

I recommend you do this annually to adjust for utility increases and other variables.

Assuming you are inquiring for the Myrtle Beach market, the average (across the 5 submarkets and all property types) is for 72.5% to require 2 nights or less (46.5% have no requirement).This is highly variable by ZIP code and property size/type, however.