Question regarding HELOC

[Sooyeon Kwon]

Hello,

Im a newbie in RI. Im still renting but considering purchasing my first home or a multifamily for rental. My question is re: HELOC.
so the percentage of HELOC is generally 80% of the equity on your property if Im understanding correctly. 

So if the value of the property decreases, does that affect the total amount of HELOC as opposed to the amount I would have gotten at a higher purchase price?

Say I bought a property for 80K with 20% down. Then within the year , assuming that the price stays at 80K, if I were to take out HELOC, how much would I get versus if the property value goes down to 70K.

Please guide me on this novice’s RI journey. 
thank you!