Title work on assignment contract

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Long time lurker, first post. 

I've come to a verbal agreement to buy a home on an assignment contract from one of those "we buy houses cash" investors. They seem legit and sent me the contract to sign, but they want me to close with their attorneys. Seller says their attorneys have completed title work and everything came back clear and that there will be a general warranty deed that can have title insurance on it.

Now, my question is I've never closed on a purchase using someone else's attorney. Any watchouts here? They say they have no issue with my attorney reviewing their attorney's title work. Maybe I am worrying about something that is no big deal, but would like some input from those of you with experience with this kind of situation. Thanks!