Consider him to be your next/only tenant when screening.It is a major newbie mistake to only consider the qualifications of a existing tenant when taking in a additional person.

I suggest you get an average for the past year, increase the rent by that amount + 10%, and just add it to the rent so you don't have to think about it.Once exception: I put a cap on how much is "included" with the rent.

We also ended up selling it as a for sale by owner with both parties which kept an additional $30k plus in our pockets.Lots of people we talk to think that we we're lucky and maybe we were on a few things like selling without an agent but I still think that you can put in more money to get more money out.

I would imagine he is referring to being all in (purchase + repairs) up to 80% of ARV (in addition, maybe he has a lender who will loan up to 80% LTV).

Now I have taken an addition line out on our house and wondering what is best with using this money for purchasing another property? 

If you can recouped your cost within 2 years with the additional rental income then the expense is justified.  

Additionally, the real estate company who sold it to me reached out and said they would be willing to buy it for 620k.

We feel like we can remodel and renovate the properties to bring in an additional $2,000/month(by turning one of the 1 bedrooms into a bi level three bedroom by taking advantage of the large pitched roof in each property.) 

Does anyone know any additional requirements?

These are professionals with additional training and a stricter code of ethics.