When I bought my first dedicated rental, my lender (a major US bank) considered 75% of the estimated incoming rent as part of the DTI calculation, but that was a number of years ago now.  

Stay dedicated and focused.

Most folks working on smaller projects are trying to do everything on a budget and smaller contractors often don't have a dedicated team to give accurate estimates and handle multiple field verification.

How many team members are dedicated solely to providing service to your clients?

To collect paystubs, driver's licenses, or any other documentation from tenants, you might consider using property management software like AppFolio or Buildium, which have secure portals for these purposes.When it comes to setting boundaries for tenant calls, you might consider using a dedicated business phone line that has a voicemail set up for non-office hours.

For a first investment property, with about $25k dedicated to put towards a property, how do most people start out?

I would be interested Saturdays are far better for me than Sundays and the third Saturday of the month from 9-nom is dedicated to the local REI group.  

Plus a lot of people invest in RE as a side gig, meaning they are not dedicating 100% of their time to it.

A consumer can, by sheer dedication to month-after-month on time payments--raise their credit score to, say, 680 but still have a foreclosure (as defined by Fannie/Freddie) to deal with when they apply for a subsequent loan.

Also, another cheeky little idea that I haven't dedicated time to yet... mobile home parks!