subject to' existing mortgage in Baton Rouge LA

subject to' existing mortgage in Baton Rouge LA

I've never done a "subject to" purchase.
My daughter wants to buy her father-in-laws house, subject to the existing mortgage. She needs to buy some time, about two years, before she can get her own financing. She lives in Baton Rouge and I have never done a deal there. Are there any particular issues she should look at? Any help and input would be appreciated.
Thanks

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