If you have any investor who invests with you where you are doing all of the work creating the return and they are expecting a return you have security, 1 investor or 1000 investors.
There are instances where you do not have to jump through a full blown exempt offering, but as was stated, speak with your own securities attorney.
As for your proposed structure. Your private lender will lend to your equity LLC, (you may have to personally guarantee the loan) but should not be a part of the LLC. They are just a debt investor.
Now, if you wanted to, you could create a lending LLC where you sell notes to different investors (yes this is a security) and then you can lend the money from the lending LLC to the equity LLC that is holding the property. That way you can have investors who like debt in your projects as well as investors who like equity in your projects.
I agree with the 1 LLC per project situation (on the equity side) just because of the issue that Rick brought up in terms of valuations. But on the debt side, you do not have that issue because you would be offering a fixed note potentially backed by a number of different properties, that would actually give the investor more collateral potentially to back the notes.