We can buy the house for maybe 125k and he estimates 120k in renovations.

I would also add, a contractor that you can buy materials for and they know how to put them in with little to know direction (reduces the management time of the project).

If you're looking to buy bigger buildings that's another ball game altogether.My advice: what investing do you feel most confident and excited about?

Or should I just exhaust the heloc and keep buying houses? 

I have been buying and dealing with Real Estate for about the last 30 years.

Depending on the type of rentals you have, pulling out the cash in a refinance might be the way to go to buy the mobile home park.

Direct buy? 

One golden rule I follow,if it takes a long time to fix/replace when it breaks, don't buy a cheap one.Imagine, this thing breaks in the middle of your peak season and the people who can come out to rebuild are 2 weeks out....It takes at least a day or two to build something like this even if you are super skilled.

Investment Info:Small multi-family (2-4 units) buy & hold investment.

Your credit at risk and might affect your ability to buy a home in the future.