There are schools all over, including Wilmington for sure. https://dpr.delaware.gov/ has all the details on schools and requirements, typically the schooling can be done online and then the test is done in person at a testing center. 

But hunting for deals in the retail pond will provide less than desired results...unless of course the investor wants to pay near retail and bank on appreciate...which of course is fool's gold. 

Are these commercial properties like offices/retail or apartment buildings? 

Quote from @Derek Morrison: You can start by researching online.

I’ve been doing that with a few market recently, I try to spend a week just online trying to figure out the different boundaries/different neighborhoods, what the dividing lines are, what type of housing stock is there (I only focus on post ww2 brick for instance) than figure what the yields are in these areas, and then decide if the yields are decent enough on risk adjusted basis to bother to invest.

Where are the best places (in person or online) to find qualified buyers for investment properties?

You are not alone in that situation as you can see a lot of online comments about people having the same issue.

I would start by networking with other investors and asking them for recommendations.Research online for agents that are busy.

Purchase price: $485,000 Cash invested: $10,000 High Visibility Corner Retail Location. 3800 sq ft, 2 story building.Potential NOI valuation (after repairs, finishing) = $1.4MDue Diligence happening now, seeking Qualified Cash Buyer

You can also check their reviews online at Google, Facebook, or Yelp.