For example, one $27/hr FT property manager of mine can manage 140 leases.

I then decided to modify my criteria to look for deals that were 50+ units and found that I had much more success in that space because most credible bigger buyers aren't looking at deals that are smaller than 100 units. 

Is RentRedi as easy to use as Avail for posting the listing and managing the listing?

I would focus on a strategy and you and your brother like (Do you want day to day management of a house flip?

Consider managing remotely you'll have to be willing to travel 3 hours when needed or find a way to handle it virtually.

I've managed up to 400 rentals and never offered a concession.

Whether you spend time networking, reading books, watching videos or connecting on bigger pockets or if you spend cash hiring a mentor, maybe partnering up with or doing free intern work for a real estate investor; whichever route you decide to go investing in yourself is one of the best investments you can make. 

Managing remotely works until it doesn't.

I knew this 4 years ago and decided to build my real estate portfolio to get enough know how to finally get involved.

Let me know if you ever need property management!