See if you can get a list of trades/suppliers seller used, for your records and contact them. 

NO reputable lender asks for funds upfront besides appraisal fee.Have heard MANY horror stories related to upfront fee lenders and it rarely ends well.

If you go with the new I’d really look into the reputation of the builder and see if you can get some references and then contact them and ask questions about anything and everything you can think of.

I am new to the industry but am focused on long term goals and wanting to build a team of reputable individuals where we can all bring each other value and make some great money together. 

If you're committed to active investing, the easiest place to start is often finding a reputable turnkey seller, perhaps even one who operates in several markets.

You want to establish a reputation for our properties going down the assembly line consistently.

I've used home depot/lowes in the past but was looking at using a supplier like Prosource to get my materials.

I suggest using BiggerPockets' "Find a Lender" tool to find a reputable hard money lender. 

I know a reputable CPA who focuses on real estate and actively participates in REI himself. 

Kiwi II is another possible supplier.