Right now I can bring all the work to the table, just need the money.  

I’m still focusing on what I can bring to the table for business relationships with potential mentors and agents, I have been reading more and listening to podcasts, etc.

I have an offer on the table for a private money loan of $310k to finance the purchase of two properties.

You tried to take them for a profit but maybe they've turned the tables on you.

I just cut it to size on the table saw. 

Getting investors is just as much if not more about what skills you bring to the table, your ability to network, how well you've managed other deals, ect, as it is 'the deal'.The amount you should save depends on what type of properties you want to buy and how much you have saved now.

We agreed on a cash offer, but I'm only able to bring 15k to the table, so I'm banking on my brother or a lender to cover the other 45k within 15 days in cash.My questions are, where do I get a purchase and sale agreement, and how to fill it out, and also how to do a septic inspection before going to title and escrow without getting burned by them backing out and keeping my 7-800 I'll have to shell out. 

Obviously I need to sell myself as well and show them what value I can bring to the table. 

If i'm renegotiating, any advice on how to come back to that table and some terms I should look for? 

If you keep massaging the ideas the right path will show itself.