This is done all the time...many businesses that you frequent in your home town are sole proprietorships, not legal entities like corps or LLCs. 

I plan on doing a few more soon.I've had discussions with my CPA and Lawyer on the subject to understand the risks and tax implications.

Write a "subject to" type of clause into the offer?

This topic is very subjective, so there is nothing definitive - only various opinions.

I think a great way to begin using BP is to read the Bigger Pockets Ultimate Beginner's Guide to Real Estate Investing as Josh and Brandon did a great job with it.And now that you're here we'd love to see you be an active member of the BP community so be sure to set up Keywords Alerts for your local area such as "Clementon" or "Cinnaminson" if you're looking to find potential opportunities for investing, education in a subject, or other members in your area.

Investigate those requirements in NJ license law.Licenses are required for the types of business conducted by profession, a company really isn't subject to professional licensing but rater those officers, directors or owners of the business entity, there are requirements for entities to be owned or operated by licensees. :)

I think a great way to begin using BP is to read the Bigger Pockets Ultimate Beginner's Guide to Real Estate Investing as Josh and Brandon did a great job with it.And now that you're here we'd love to see you be an active member of the BP community so be sure to set up Keywords Alerts for your local area such as "Brooklyn" or "Flatbush" if you're looking to find potential opportunities for investing, education in a subject, or other members in your area.

I haven't found any books on this subject either.

I think a great way to begin using BP is to read the Bigger Pockets Ultimate Beginner's Guide to Real Estate Investing as Josh and Brandon did a great job with it.And now that you're here we'd love to see you be an active member of the BP community so be sure to set up Keywords Alerts for your local area such as "San Jose" or "Mountain View" if you're looking to find potential opportunities for investing, education in a subject, or other members in your area.

Many times posters put one word in the subject line, or it's so generic that it draws no interest.