They can be legitimate, but they are not the preferred way to go.

I plan to buy my first house in 2019  would really like to house-hack.Ideally, I would prefer a house in Long Island but will be willing to settle for Queens, depends on the neighborhood.What are your thoughts on buying a single family and convert to multi-family for hacking?

If we can do a HELOC on our primary that would be preferable. 

When they realize that you are not going to allow them more time, they will find somewhere to live, even if it is not what they would prefer.

As additional perspective, I'd prefer to invest in or near my local market (Raleigh, NC), where is VERY tough and competitive to find multi-families!

What do you want to invest in next (your niche)? 

I would prefer not to do that if possible, because I don't want to expose myself during this brief vulnerable period without protection, but I also don't want to break any laws or LLC shields if this process is not handled correctly.What are your thoughts?

Any ideas on how I can find a teardown preferably off market?

VA loans don't typically include cash-out for remodels, but I believe there are some niche exceptions such as energy efficient upgrades.

There are tons available, usually free to the Landlord, and it's just a matter of trying several and determining which one you prefer.