Rent was due by 5th but no communication on late payment and is not responding to my text/emails. 

You might get these days 60% leverage so you'll likely need 40% down payment plus reserves and the financial institutions will want you to keep those capital reserves in their institution.If you are a new investor, there's a couple of opportunities to get started. 

Financing: I'm confident I can put $10,000 down as a down payment within the next year.

What % of purchase price is smart to put as a down payment? 

If it’s verbal, they’ll need to document any prior communication or payment records to establish the relationship.If the PM is completely unresponsive, they may want to send a formal written demand for communication and payments via certified mail.

I know that when I’m buying a loan, I’m buying the future payments at some price.

What property management software or tools would you recommend for tracking rent payments, leases, and maintenance requests?

What you spent on the land/lots can go towards your down payment and, if you've owned the land for more than 6 months, you can use the value of the property toward the cash injection requirement.

We will either bring on another investor each year to make the yearly payment or we will just forgo the income payments to the partners and make the yearly house payments out of the cash flow if we just want to keep the property with only 7 investors. 

I use Buildium for tracking rent, fees, leases, and collecting online payments, but I don't use their reports for much, as I end up copying my online banking each year into spreadsheets.I've been using Rental Hero for the last hour and already impressed with it.