@Ned Carey It never made sense to me. 

Makes sense.

That makes sense.

You want to make sure those numbers make sense, too!

They make sense when you sometimes need the money, sometimes don't as you don't pay interest when nothing is drawn on the HELOC.  

me and my sweetheart have enough for the down payment on a duplex. we want to save to install a granny in law suite in the attic. just a studio unless the numbers make sense for more of course. from what I researched it can run me 32k to 65k on the cheaper side if I can use unused space.our goal with it is to build the studio then live in the studio while househacking and renting the large units then when we save up for the next duplex do the sameAnd just rent out the studio for 5 600 after wardsturning the propertys into suido triplexes.any problems I may run Into trying to do this?

It makes me want to just jump into the first thing that makes sense.

I find that a very common hurdle that beginners have is assuming what a lender will or wont do. you said "I don't even think I would qualify for a loan of 100K" which may or may not be true, but you don't KNOW. what you really want to do is ask a lender what it takes to get that loan, rather than assume you can't get it and then blindly try to improve what you think they need. does this make sense?

Chris, Makes sense. 

I could purchase a home on the otherside of town for around 90k in cash and live there.what makes the most financial sense?