I'm buying a house cash and using the seller's agent. Is there anything I should look out for?

yes absolutely, Check to see when the house was last sold. If the seller has only lived in the house for a few months or less, you should inquire as to why they are selling so rapidly.

and 

Examine the house's construction materials. Concrete houses, particularly those with steel frames, are considered non-standard construction, and many mortgage lenders refuse to finance them because of a variety of possible flaws. If you plan to buy a concrete home with cash, you need to have a professional survey done.

Yes, you can use the sellers agent. Just understand the seller Is the only one

being represented. As a member of the Realtor’s Association the realtor is 

obligated to present you with all the 

standard documents & addendums 

that pertain to the sale and adhere to 

all laws that pertain with the highest 

standard of integrity.