Best way to use HELOC with decent equity in homes

[Manish S.]

Here's what I have (conservative estimates below):

Primary home and Rental home: 1.5 M in equity (900k+ and roughly 600k) 

Income and Liability: I am self employed now for over 2 years, not have a consistent income. My income and liability today will not support another mortgage of 500k.

I am now planning to purchase a land and build on the land. Land cost will be roughly 300k, and construction cost will be roughly 700k (probably little more). I desperately need some creative suggestions on how to make the best use of my equity with the least monthly payments. The best method would be to have no payments and fund my project with equity and then pay it off in one go when it is finished. The project will last for 3-5 years, so I will be paying interest for a decent amount of time before I see any profits. 

Looking forward for some expert suggestions