The deal involves buying an existing single-family house for $700k that conveys with a vacant lot.

I just checked Google Maps, and apparently the development is in Hazel Green, just off the 431. 

I would LOVE to develop this land myself and sell a house, I simply don't have the capital. 

Balloons coming due with higher interest rates, China market, China production, Manufacturing production moving back to the US, Worker shortages, Workert pay hikes, Ukraine/Russia food and fertilizer misses, Oil prices increasing due to the OPEC Q1 production curtailments in place, Houthi issues, Panama Canal Water issues, Illegal immigration impact (buy one of those office buildings and rent for $10mm per year for Illegal housing, take advantage) social benefits required, Climate change believe it or not- Buy or sell into that thought process,  US politics, Baby boomers leaving workforce and needing more benefits, Baby Boomers moving from Stocks to Bonds,  etc.I agree things will get worse, but that means more investing opportunities. 

I just got the notification from the city that there is a new apartment complex that will come up right in front of my house.

Not aware of how construction cost are looking in Milwaukee, but I'd talk to a couple of contractors/developers in the area.

Just think about the worst damage a tenant can cause, such being liable for setting your rental house on fire or burning down your rental house and the neighbor's house, etc.

Furnish Finder, corporate housing sites, relocation companies, etc?

There is also plenty of other ways to get business, you can do open houses, use social media, door knock, etc.

You need to calculate your return on equity to see if it’s time to leverage that equity more, you also want to calculate your blended interest rate of the original loan and the the HELOC to see if that’s the best rate or if a cash out refi would be better.If I were you I would look at doing the same move again and buy another primary residence and turn your current house into your second rental.