Simplifying Deeds of Trust and assignment of rents

[Chris White]

Hi, 

I'm not from the US and trying to get to grips with deeds of trusts for a story that I'm writing.

I'm investigating two properties which have a long history when I look on property shark.

My first question is can a property only have one deed of trust at any one time, as one of the properties I've looked at has had three deeds of trusts in the last seven years. Does this mean that the owner has paid off the first two loans and is now on a third? 

If a property has a new "deed of trust and assignment of rents", does this mean that the owner is definitely renting the property out - or does it give the owner the option to rent it out if they want to? 

Many thanks for any help