This would obviously reduce my cash flow on both properties, as I would be paying the minimum HELOC payment plus extra towards the principal to pay it off quickly.

The least states:"Tenant shall pay a "late charge" not in excess of five (5%) percent of the amount in arrears for each month the arrears remain unpaid if any Rent is paid more than ten (10) days after the due date thereof, to cover the extra expense involved in handling delinquent payments.

Some of this may have been grandfathered in, but now need updating.I would pay the extra say $50,000 to have an Engineer firm go over.

Early on in my career, I saw a close frend do something similar.. she borrowed from her circle to finance a rural fixer-upper, then paid them back once she refinanced after the rehab.I’m guessing that massive yard plus the barn is already a big selling point for your tenant, especially with a family that wants a little extra room for animals.

The only big issue I ran into is on of the basement walls needed extra support, I don't think a newer build would have that issue. 

I think the big question is how badly do you want to keep the extra $50k liquid?

With an extra vacancy or a maintenance issue or an extra turnover, this is definitely a negative cash flow producing investment.So when you say the rent growth and value growth have exceeded your expectations, I would love to have you respond as to how that is possibly the case. 

The reality is the opposite - if it's not in writing then the PMC doesn't have to provide the service or can charge extra for it!

Most investors let the tenants pay down the mortgage and use extra money for their down payment on their next rental.  

This extra road frontage now also qualifies my property to be able to be legally converted into a triplex from a duplex.