Rent out MIL's vacant house (first time landlord) instead of sell

[Jon Flash]

My mother-in-law has moved into a retirement community. My wife and I were originally considering selling the house to cash out in this sellers market. The house went on the market, but the deal fell through (MIL got ~$4,000 in earnest money from the buyers backing out). We expect her to net $40,000 - 50,000 on the sell of the house (after accounting for closing costs/realtor commission).

Now we have the option to rethink the sale of the house and instead consider renting the house. The mortgage (plus taxes) is $700/mo and Zillow puts the rent estimate at $1,400. What is the best way to figure out potential rent for the home? I don't expect to get $1,400/mo, but I also don't know what I don't know.

What are other things to consider in renting out our MIL's home? I would assume she remains the owner and we (her daughter and I) have some signed agreement on managing the property. The primary goal here would be to cash flow money to our MIL (she needs the money as her budget is tight).