With that in mind, I’m considering purchasing four rental units over the next four years to build a stream of income that could help supplement my retirement by age 68.The challenge I’m facing is that the deals I’ve come across so far don’t make financial sense.

Very challenging if not impossible to make lot ratios work if the existing property isn't conducive. 

I know some might disagree.The challenge is if someone applies and meets all your criteria and you reject them, I would hate for you to end up in some legal hot water.

Stability: Homeowners tend to stay in their homes longer than renters, which can create a more stable environment for families and children.

Thirdly, financing and potentially selling later on could be challenging again with the part of the plan being on a campground. 

(I work with some challenging populations and the extra effort has paid off in these situations.) 

Quote from @Michael Smythe: We're far from perfect, so our 2 cents should be taken lightly.Most of the national companies are setting up franchises and the challenge is with the individual franchisees.

A cosmetic rehab is still quite a challenge for the first time.

Challenges?

When I return to the country after my Au Pair contract ends, I hope to live in the property as my primary residence and house-hack as well.I understand that investing remotely makes things more challenging, but I am also ready to be uncomfortable and challenge myself in this journey as I know it is 100% possible.