Given that you've been carrying the property without a tenant for four months, you're already feeling the strain, so let's break it down:Long Term Rental vs.

For example, single-pane windows can make heating and cooling more expensive compared to double-pane windows.

The seller and I could not come to terms over an issue that arose in my inspection regarding upgrading one electrical panel. I

I could also borrow some funds from my parents but not sure if I want to do that and put strain on them. 

Installing small things like a heat pump and insulation with new double or triple-pane windows for snow regions.

If they don't renew, I'm forced to start a no-fault eviction, which strains the landlord-tenant relationship.

It might put a strain on the relationship, there are other things to line out though, that is just one item.

Will it strain your marriage/relationship/family life to a breaking point?  

Given that, I changed to getting pre-cut SIP panes and building myself.

Some wholesalers have been known to engage in less-than-transparent marketing strategies to secure a deal, further straining the relationship.Questionable PracticesSome wholesalers may engage in practices that realtors deem unethical, like purposefully seeking out financially distressed homeowners and pressuring them to sell at prices well below market value.