I've been selling products on ebay for some time, so I have some income coming in.

The purchaser takes the property charged with the primary liability for the payment of the prior mortgage and must therefore service the prior liens to prevent loss of the property by foreclosure of the prior liens.”https://www.jimersoncobb.com/blog/2012/08/special-considerations-for-bringing-a-foreclosure-action-by-a-junior-lienholder/

I am the product of a failing school system.

Any kind of real estate that has been held with the intent of holding for productive use can be sold and exchanged for any other kind of real estate that you intend to hold as an investment. 

But if you're looking at smaller deals (sub-50 units), syndicating might result in a higher cost structure as you'll have to deal with lawyers and specialized accountants.

I need a real estate line of credit product for those of us who know what we're doing and need to move quickly, with reasonable flexibility! 

BUT your down payment is SIGNIFICANTLY less than any other loan product....well, almost any other loan product. 

I have four (4) duplexes in Baltimore in my name and want to transfer ownership to an LLC I formed, so I have the following questions:1) Do I have to use an attorney as opposed to a specialized entity (title company and such)?

If you can't pull that out, then it may be in a Policy/Procedure document which you will have to make a special request for.2. 

You cannot 1031 into properties you already own or to pay down a  loan on a property you own.You're lender is probably giving you a partial release when you sell in exchange for a certain % of the net proceeds from the sale of the one unit.While it is conceivable that you could do a 1031 on this sale I think you need to look closely at the issue of intent.  1031 is only available for properties you have purchased with the intent of holding for productive use.