Let's say I buy at tax sale, I want your rehab money 30 days later, would you lend to me for the rehab without security of the property?

Security Deposits / Escrow: If you would like to use Baselane for an escrow account, you can simply open another sub account that is separate from your day-to-day activities.

Security deposit amountYou can find plenty of examples by searching for "tenant estoppel certificate doc" or exchanging "doc" with "pdf" for more options.Here is an example and explanation: Sample EstoppelSome have a lot of legal jargon but this document does not need to be so detailed.

Borrowing from multiple investors on one note creates a security that likely requires a registration or some other form of exemption.

It is cheaper, easier and more secure. 

Second example: I purchased a first lien note secured by a very run down shopping center in which the principal balance was $470,000 - I paid $255,000 for the note.  

Give them 24 hours to pay the security deposit and sign the lease.

This could signal that buyers are embracing low-interest rates and turning to financing to secure their dream homes.

I noticed you are a lender who operates in my state as well, if you have some time available I think I would greatly benefit from learning what I can be doing to increase my chances of securing a loan and what lenders look for in potential clients. 

If you only have 25% equity in the other property and no cash, then that probably will not work as its too risky for the lender unless you also have other properties to secure it with.