Best practices for finding funding?

This was reported by the lender and the lender eventually fund the loan.

I could keep all my funds in my conventional IRA and then when I retire I could take the tax hit on it then.

Since you'll likely be borrowing money to fund any future deals, you should make it as cheap as possible by getting that score up.  

Would a private money source fund a down payment on a buy and hold property?

I need funds for a flip or a quick cash out finance to get extra funds to throw down on my next move. 

My wife and I  have a decent income, i'm a firefighter and she is a cosmetologist and we had been saving money for a while and had been keeping it in mutual funds.

In the unconventional lending world there is no specific period you are required to wait to be able to refinance based on actual appraised value, which means you may be able to refinance and cash out your original down payment funds and potential lever equity immediately following rehab completion and tenant placed.  

As long as this is the only hair on your file to purchase the primary residence a bank should fund your deal.  

From there, I would have to find different funds to start investing with.