I wonder why they don't make roofline sprinklers or some other product like that. 

Much better than average location3.

In Berlin, rental arbitrage has been very profitable, with average annual margins of 25-40% after all costs but before taxes, so shifting to a market where arbitrage is barely breaking even is definitely a reality check.Given your experience, would you say the best way to enter the market now is through purchasing properties with financing?

We’re fortunate to have an above-average income and live well below our means.This summer, we’ll be moving to Detroit (PCSing in August), and we’ve saved about $120,000 to invest in addition to having funds set aside for the home we’ll purchase in Detroit.The reason I’m posting is that I’m struggling to decide how to best allocate the $120k.

If rents go up ONLY LT historical average (4%), NOT post covid averages (post covid was 20%+ annually). 

What is the average acquisition cost of the houses?

The differences between most software is subtle and may be how they bill for their service, support their product, or the process to use those features.

All programs have LLPAs but that's more so any bank's individual guidelines and overlays to specific product pricing.

Take the average household income in an area of working class residents. 

On average we have spent about $60k to reset the clock on a 1960's single family home.