And again at the risk of sounding naive & being real honest here... we know nothing about building, seemingly, it wouldn't be too ridiculously expensive to build say a rectangular 1500 ft² house on a slab where all you really had was an open kitchen to living room and then on either end of that a master with a bathroom other end 2 bedrooms with a bathroom in between.The main thing which, I know is probably the most cost (and this is going from an amazing airbnb I stayed in with girlfriends called the skyhouse, which I zillowed by the way worth $650000 our budget only about $350 K)We want both sides of the big main room (kitchen & living room) to have  Florida ceiling collapsible windows so that you can have a complete open field in the good weather.A pool would be amazing but can come later.HELP???

Just let it sit or try to put it in say, a REIT or something until I’m ready to buy?

This starts with a number for your market that works, so say a paint and carpet rehab ("lipstick") is $10-15/sqft of the house.

Often if you go to the cost seg company you end up paying the same or less and some of the companies include audit defense for free in their overall price charged versus the accountant subbing it out to them to do the engineer part if there is an audit the accountant will charge usually per hour additional money to defend.There is nothing to say you have to sell all those houses you could sell some and then buy say a 3 million type property NNN.

That said, I may not be the best to say as I've only got 2 units currently. $20/month for Water and Sewer is likely too low as well, just noticed that, unless you're somehow splitting it with your two roommates, but even $60/month seems low for 3 people.

If it is say a new construction or something, if its expected to be valued at 100K, the lender will provide 90k.

Or do I need say a third party to witness?

Photos and description on listing, assessor card, past listings + listing history (Hotpads, Zillow), tax bill combined can say a lot about the rehab numbers, problems with the prop, and seller motivations. 

Best first property is usually not raw land, I'd say a relatively inexpensive SFR or duplex if you aren't going to be living there or a house hack up to a 4plex is probably going to be your best starting point.

Personally, I'd use the HELOC in projects where you know you have a reasonable chance of getting your money out quickly (say a BRRRR, maybe a quick flip).As the adage goes: "Live where you want.