My daughter is interested in house hacking and I would like to help her out. 

You don't want a situation to occur where daughter gives notice and moves, but now dad has possession (with whom you have no legal contract) and is not paying rent. 

I'm thinking about purchasing my mother's home as my family consisting of me, my husband and daughter have been living in it and paying the mortgage the last 4 years.

First off, Thank you for your service, My daughter is in the military also, she makes me proud. 

My daughter and I will be doing this together.

I spoke to the daughter of a property owner whom I had lost spoken to about 3 months ago, her mother unfortunately has recently passed and now she wants to sell the property on her behalf.

My daughter will eventually grow up and reflect back.

I fully intend to rent out several of the rooms, possibly in a Short Term situation through AirBnB type sites, some rooms to what I hope to be my daughters college friends that have Mom & Dad to foot the bill for them :) Aside from that using a small MultiFamily is a great idea as well as even doing a live in fix and flip, these are all ways to house hack and unless you just can't stomach having "roommates" or living next door to your tenants then I just can't see a downside. 

When I went to make the offer she stopped me and said that she needed her daughter to call me back. 

The most important thing has always been security for my Wife and daughter.