$300k cost is me eating some of the labor I'll do. 

The more kids in a building the more it’s going eat you your money one way or another it’s going to cost you .

If he is leveraging your down payment to borrow the money.... first, you are going to have interest costs eating into that profit margin.

Carrying costs will eat you alive.The longer you hold on to the property, the more stress builds up.Visited the town planner to ensure that nothing "big" was planned - new road, new development, gas station etc.

If you can avoid FHA, it's usually a good idea so you don't have to eat the PMI for any longer than necessary.

In other words, as a new agent you still "need to eat".If you are with a company that specializes in only Multi-Family but they are a brokerage you have never heard of then there are some challenges with that.

Probably be around 10-12% interest plus points which eats profit.I would network and find private financing.

Granted, the holding costs as you rehab will eat some of your profits but you can use the conventional financing to overlay the remaining loan.

Am I responsible for paying him for these expenses or should he be seeking these funds from the bank that declined the mortgages or would the title insurance company eat these costs?

It will eat batteries for non AC powered devices, but at least you have time to fix the hub issue.