For your long term success it does not matter as much if you have 10 doors or 100, as if your portfolio value is 500k or 5 million. 

Tenants don't read the lease and if they do they forget about the details soon after.Instead, post something like this on the inside of the bathroom door:

If your intent was to hold onto the property and a bear moved in next door (True Story) or maybe you receive an unsolicited offer you couldn't refuse, so you decide to sell.

Enhancing the exterior with fresh paint, landscaping, new siding, or an upgraded front door can create a strong first impression.

that we’ve learned in our 24 years, managing almost 700 doors across the Metro Detroit area, including almost 100 S8 leases.

Initially she was very happy and excited but after a day, she had a disagreement with the contractor and now she's not opening the door for the contractor to come in and finish the work.

Both have strong fundamentals, good schools, low crime rates, and job growth → which are critical drivers of long-term property value.

I'd recommend doing some research into what markets you want to target (landlord friendly / growing population / economic drivers and developments) of those markets. 

If there is just a smart lock on the door I don't think they need the key.

I'm planning on quitting soon, moving back home for a little and taking a few months in between my next job to pursue my first investment.My rough idea for an investing strategy is:  long-term, not necessarily looking for high cashflow (just want to start building equity), quality deals > amt. of doors, Class A/B neighborhoods mainly for low vacancy.