Im in the process of forming my LLC (long term rentals is the goal) and would like to know if the forming of a “domestic eligiable entity electing to be classified as an assotiation taxable as a corparation” is correct for what im trying to do, Im also going to form a s corp for the purpose of flipping can i form the s corp under the same LLC? 
many times the LLC is a disregarded tax entity. There is a test in the IRS forms to figure this out.
check out www.irs.gov
If you have a single member LLC, it can be treated as a Sole (disregarded), or as a corporation (you also need to elect S if you want to be treated as an S).
If you have an LLC with 2 or more members, then your choices are to be treated as a partnership or corporation.
For holding property you are probably better off not being treated as a corporation.
For flipping it seems experts will suggest an S corp.
Good Luck!