Subject to deals or double closing

[Kanekalon Kindle]

I'm a Realtor and my husband & I are looking to get started in RE investing.  I have a seller that wants to get from under the home.  She has a tenant that pays here & there. The owner stated she pays the mortgage one month and skips a month due to the way the tenant pays her. She owes about 41k, she's not quite sure how the homes like on the inside now.  I pulled comps for the area 2 homes sold within the last 4 months. One home for 57k and the other 69k. I'm not sure with a situation like this if I should do a subject to or double closing.  A friend of mine has an investor that loves to buy in that area because they own several homes.  They also have the cash money to buy now.  Can someone let me know the best route to go?  We do not want to make the wrong decision.

Thanks!