I cannot afford another above the $16,000 which is why I told her $15,000 was the budget.I also stated to let me know of any extra charges that come up so I can watch the number.

And that extra $40-$50k a year will be life changing.

In the case mortgage foreclosure, I usually offer to pay for the existing mortgage and give them a little extra to move.

Adding mass to the walls works wonders—attach Mass Loaded Vinyl (MLV) to the shared wall, then cover it with a layer of 5/8” drywall using Green Glue soundproofing compound for extra noise-blocking power.

Should I take extra steps to verify their identity and legitimacy?

You're correct, many investors think that using an experienced agent is just an extra expense.   

then theirs charges 1000s in extra fees. 

There is no additional "risk" on the note like a demand clause etc, but you have  extra expense in upfront one time costs and the pre-payment penalty that most programs are sold with if rates do drop as expected in the future.  

Quote from @Caleb Brown: Someone else asked but what would market rents be including the extra storage?

It may sound nice to pay a 6% management fee but the extra fees can add up to be more than the other company that charges 10% with no additional fees.