My interest is owner/occupied fourplexes in which I can spend a year to gradually update each unit.

Furthermore, I think rather than pay for tons of leads from multiple services, real estate professionals should invest that money in their brands, websites, networking, and gradually develop their niches.

I plan on starting with small multi family homes and gradually move wherever that road takes me.

You may want to gradually build up a few more lines.

Super-low mortgage rates and the growing prospects of our economy gradually returning to normal are likely to keep demand high.

Because they didn't have a predictable business with consistent lead flow (No lead flow = No Closings) For now keep your overhead low - keep doing what your doing and study your KPIs, keep track of what marketing works and what doesn't, gradually invest a bit more into your marketing channels and have reserves for yourself (expect dry weeks/months with no closings).

As for rent increase, in my 30 yr cashflow model I am assuming inflation at 2%, so any rent increase under 2% will begin to show a downward trend as my costs gradually increase.

As much as I want to rush this, I know it is a gradual process.

But I don't think you can own 30 existing properties and gradually cost seg them over several years in groups of 5. 

(oddly though they hadn't been monitoring value over the past 3 years and recommending raising rent gradually until I brought it up)  Anyway, they confronted the tenant when they paid their rent and told them that rent was being increased by $150 and if they didn't want to pay the new amount, they could vacate by the end of the month.