I’m wondering how to structure my foundation.

You can structure the loan in the 3-4% with local banks if you have strong tax returns/financials/experience/credit.

I would probably verify with local zoning authorities as far as any structural changes needed to the façade of the exterior to allow for a separate entrance but that is likely not an issue in most cases. 

The key issue in structuring a partnership is correctly placing the risk for unforeseen events. 

A lot of things to consider; you need to make sure you have identified a market that suits you, understand its dynamic (net migration, economy, Crime etc...) and then have your criteria fully defined: What type of property, size, what is your business model, what perfs you want, how you are going to structure the deal (JV, Syndication)?

@Zak Marinko as an investor/agent you need the right structure that will allow you to do deals the way you want and make max profits. 

Frankly it makes the deal less valuable to a buyer (as I said no one wants to take on his single user or like an S Corp structure)

If there is an issue for local law, we can coordinate local counsel, but most structuring entity formation is not needed.

A multi-member LLC is taxed like a partnership anyway by default.the business structure is an exhausting discussion. 

My concerns are that there might be some structural damage only in the sunroom.