One of the biggest challenges is keeping the bathroom as carefree as possible.

On a related note, I would say that the biggest issue that small investors face is underbidding.

You haven't even asked about your BIGGEST challenge - finding "trustworthy" contractors.- Most contractors will cut corners, or worse, once they figure out they won't be watched closely:( Your job will also go to the bottom of their priority list.Monitoring progress is relatively easy: hire that same inspector to go by weekly or before any payments to take a VIDEO of:1) What was done2) Quality of workmanshipOne other thing you didn't ask about, payments to contractors.- They all want 50% down or as much as they can squeeze out of you. 

But it’s clear you’re a smart investor who knows the long-term benefits real estate can bring.I keep reminding myself why I stick with real estate: you can make money every month in four different ways:Cash Flow – Passive income to live on.Appreciation – Long-term property value growth.Depreciation – Tax benefits that reduce your taxable income.Tenants Paying Down the Mortgage – Even if you’re paid off now, this is one of the biggest wealth-building tools for leveraged properties.It sounds like your main struggle is the stress of active management—and trust me, you’re not alone.

That might be the biggest hurdle - but otherwise, I'd check out "DSCR Loans" which are the perfect option for people like you looking to buy rental properties w/o W2 or DTIWe don't own any other properties other than the investment property we just purchased.

What have you seen make the biggest impact ? 

Stick to these tools, and you should be significantly happier with your next renters  Thank you, I did screen all aspects and everything looked good in the beginning but the biggest problems seems to be the renter big off more than they can chew.

The biggest tip I can recommend is patience.

I recall reading in Forbes that major foundation fixes can add surprising value, becuase it addresses the single biggest fear buyers have.. a shaky structure.From my three decades in fix-and-flips, Ive noticed how important it is to have a team you trust.. from attorneys who know probate deals to realtors willing to drive for dollars with you, scouting hidden gems.

My biggest concern with ADU’s on single family lots is that all the new laws have muddled what the long term value looks like, and most people don’t realize it yet.