When to approach the lender?

[Abraham Anderson]

I'll try to be brief, here's the background;

Last week I was shown a 40 unit complex which I'm very interested in; at the moment I'm waiting on the rent rolls, but even if the pro-forma is off by ~10% it still looks like a great deal. The asking price is 1.6M

The current mortgage on the property is with a local credit union, they are interested in keeping the loan & they gave me the lenders information.

In order to finance the down payment, I will be using two sources: I am selling some property next month which will result in about ~130K in cash, and I also own my office building free/clear which is (currently) valued at $150K. I have done about $30K in improvements to my office, so I can definitely get this number raised some.

My question is; When should I approach the lender? If I'm getting a HELOC or HEL I know the process takes a while, and I should probably get this started, but I don't want to jump the gun, especially since I haven't done any negotiations with the seller on the price (and the lender/seller know each other).