Buying the 4-plex next door off market

[Andrew Katz]

~1 year ago, I bought my first property, an owner-occupied duplex through a conventional loan.

I share a driveway with the 4-plex next door, and I'd like to buy it [off market] through an owner-occupied FHA loan (i checked with a lender and this is possible).

I have the owner's email and phone number, and I've spoken to her in the past. How do I approach this? Do I just send an email that says:
Would you be interested in selling XZY property?

Since I'd be buying this property off-market without a realtor, I assume I'll need a lawyer. What types of lawyers handle these transactions?

What else should I look into?