Help with 1031 Exchange with Home line of credit

[Jennifer Lee]

Hi BP

I would like some help with this example:

we have a condo in boston we Bought for 475K

for simplicity (we no longer qualify for the tax exemption of $500K as spouse)

my agent called and said that we can sell at $900K (assume prefect world)

we have a home line of credit of 300K that we have taken out to flip a duplex in pittsburgh.

we are thinking of doing a 1031 Exchange: what would out math be?  what is our NET SALES?

$900-$475K+ closings = 425K-closings?

or 900-300K (HELOC) + closing = 600K-closing?

what is the amount I need to reinvest in 1031 exhange?