Hey there Ricky--
I think the question you are asking is what is the maximum Combined Loan to Value available to leverage your home equity to. It depends on where you live. In markets that are labeled as "declining" the maximum LTV I have seen is 80%. I have yet to see a maximum loan to value HELOC in California greater than 75% CLTV--but that does not mean that there are not small banks that will not lend higher than that. CLTV means "Combined Loan to Value". That means you take the loan amount of your first mortgage + the loan amount on your 2nd mortgage and divide it by the fair market value of your property. That will give you your CLTV.

ADeclining Property Value Area as deemed by the following:

A) Automated underwriting systems from Fannie Mae and Freddie Mace return a declining property value notice

B) Property falls into MSA, CBSA or Zip code considered a declining according to the written guidelines from PMI companies.

C) Real estate appraiser notes property as located in a declining market.

If you are not in a declining market--than good for you ;-)
Seriously though, if you are not in a declining market, I have seen CLTV's as high as 90%.

I think there's one more piece of data missing here, which is what's the loan-to-value ratio on the house?

That is, how much equity -- in percentage terms -- do you have in it already?