Recommendations:
You can build a small sub-division with 40 SFR (Single Family Residential) homes on both Lands totaling 7.70 Acres at an average cost of 200k per Unit approximately whereas the Sales Price may be upto 300k.
To start with this project, you can build 20 SFR homes initially on (LOT 11-R 3.83 ACRES) the land that is vacant and start selling those first before launching the 2nd phase.
Meanwhile the vacant building on LOT 9-R ACRES 3.87 might be used for a Senior Living (+55 Yrs) or an Assisted Living Project which are getting quite popular these days because on increased baby boomers (people born between 1946 and 1964) population.
Your Architect can make plans accordingly. Please let me know if you need any further info.
Don't contact the seller, they would llike to not receive! Reach out to the broker about the property.