Why would I be cash flow negative and losing money for years and years?"

In some cases, after crunching the numbers, the profit margin was so slim—or even negative—that I had to pass on some promising opportunities.Here’s my situation: I currently own two properties—a primary residence and a rental property—both of which have substantial equity.

With 5% down payments and all the expenses deducted, there seem to have close negative/only around $100 cash flow each month.

Just responding to your negative comment.  

Additionally, they have another property which has appreciated in value, carries low interest rates, but has negative cashflow and essentially feels like it just locks money away.

Just remember: most negative reviews are written by problematic tenants.

Mostly people with minimal RE experience are adding a single ADU and they often make that choice based on cash flow without taking into account the negative equity position.  

What some people on BP don't seem to understand is to stop making the assumption that everyone is not working their best at thisif you have to provide negative comments or any sort of negativity when providing advice, then advice or recommendations shouldn't be your fortéAs i mentioned before.

Also, focus on 2 years of job/income stability.Class D Properties:Cashflow vs Appreciation: Typically, all cashflow with little, maybe even negative, relative rent & value appreciationVacancy Est: 20%+ should be used to cover nonpayment, evictions & damages.Tenant Pool: majority will have FICO scores under 560 (almost 30% probability of default), little to no good tradelines, lots of collections & chargeoffs, recent evictions.

I do not care what the source of the return is  Historically the highest return is via a value add and appreciation and is more so recently due to the recent rate increase versus earlier this century (before 2022).However, most new RE investors cannot handle extended periods of large negative cash flow.