Do I just ask my property manager to get them to sign an addendum to the lease and if they do not sign, evict them? 

The answer is clear follow your lease you both signed to the agreement so have them follow suit or file for eviction for violation of lease.

A smart agent will sign you to a buyer's exclusive agreement so you won't have a bunch of agents showing you and wasting their time and gas. 

If the property was listed on MLS the seller probably signed a contract to pay commission and may not be able to get out of it. 

However, I suggest reading the company's website and Google Reviews when narrowing down your selection.

So decide first whether you want to be active or passive investor and start researching niches within the selected category and going to local REI meetings.

Signed a contract with contingency about cost of liens and sent to title company, and also signed an assignment to a group of Hispanic investors (including race because of the language barrier).

Will I be needing any additional forms for this as how can the owner sign a lease option if I or my buyer doesn't even own the property yet?

What do you feel are the most important factors when selecting a bank?

We inherited a tenant when a seller signed a one-year lease on a vacant unit two days before our closing.