Having the seller carry a second is not a problem for the first, as long as their business with you is finished and the loan has closed.

On the other hand, if you're aiming for long-term rental properties, getting prequalified with a lender specializing in traditional loans or DSCR (Debt Service Coverage Ratio) loans is key.

Many pest companies stated this was the worse infestation they had ever seen.Despite its condition, the property presented an attractive investment opportunity due to its below-market listing price.

Your loan would be on a different property so no financing on the property you are buying. 

I plan to offer owner financing to others that can't get a loan.

I have 9 loans currently so looking to do a conventional loan on my next depending on that process.

Quote from @Jaycee Greene: Assuming you pay asking price, I'd estimate the down payment for something like that using a hard money loan (HML) would be around 40% of the purchase price and your monthly payment would be $2,600 with an interest rate in the low 7% range (probably need a 700+ credit score to get that).

House hack another property with a low down payment loan and use the remainder or the proceeds to either renovate or purchase another investment property?  

Unless it’s specified by your loan type or lender, you don’t have to.

OO loan seems like real long shot.