Before you move ahead is there a particular reason why having this commercial space is important to the project or are you building this design because that's what the zoning requires?

For under $300k, both shipping containers and modular homes can be great options—modular might offer a bit more flexibility with design. 

Too new for results, yet feel pretty comfortable, after meeting some of the employees, and meeting Janet, all are very genuine and are appreciative, not pompous. 

That can usually be some comfort.  

Our understanding is that if we designate the $60K as "OPTION CONSIDERATION" - these funds and the USE of these funds are NOT Taxable to the property seller UNTIL one of two things happen; # 1 the OPTION gets exercised, or # 2 the OPTION gets cancelled.

Full disclosure, I recently started coaching rehab for them since I have 20 years experience in remodel and design.

I’d recommend reaching out to a local architect or design-build firm who has experience with both home additions and ADU construction to help bring your vision to life.

Conventional financing is geared and regulated for the owner occupied homeowner and is designed to protect that borrower from poor lending practices.  

The more comfortable you need to live, the worse the numbers will be. 

If you’re not comfortable with your analysis and still want to pursue the purchase, I would recommend engaging the services of a real estate consultant holding the CRE designation and paying them for a short form report.