If they fail, I continue marketing it to others. prior to occupancy, they must pay the rent for that month in full with certified funds.

In my state, the Seller must provide written proof of receipt to show it was received by the Seller.Either your agent is lying to you, your agent is failing to properly contact the seller's agent, or the seller's agent is specifically ignoring your agent.If you believe your agent is doing everything right, have them contact the seller's broker and explain what's happening.

But folks fail to realize that one can protest taxes and there are companies that do just that for investors and citizens.  

While I've been happy with his performance, this last month they have failed to pay me my preferred return.

The test consists of 4 elements:It is an investment of moneyThere is an expectation of profits from the investmentThe investment of money is in a common enterpriseAny profit comes from the efforts of a promoter or third partyIf you are borrowing money from someone it generally fails the third element above because there is no common enterprise for those contributing the labor and the capital. 

Louis if the tenants fail to pay the lien gets placed against the property and not the individual.

I’m excited to get started but I read somewhere that a lot agents fail within their first year due to picking the wrong broker.

They fail to take into account property management cost, maintenance cost, and capital expenditures.

I'm too scared to try out of state investing as I failed on my last attempt(made some rookie mistakes and learned a ton).But then I hear other option like funding someone else's deal or partnering on a deal, which outside my comfort zone as well but always willing to learn. 

Guess what, in this business you ARE GOING TO FAIL.