In it, he says there are four tax categories for landlords: business owner, real estate investor, dealer in real estate and not-for-profit (p. 38).

I moved a police man onto property gave him free rent and it drove off my drug dealers!

While the requirement was never enacted by Congress, it does provide a good indication of what sort of holding period Congress would consider sufficient to meet 1031 Exchange requirements.Dealers Do Not Qualify for 1031 Exchange TreatmentIf you are considered a “dealer”, you will typically not qualify for 1031 Exchange treatment because you are technically holding the property for sale as “inventory” and thus not for investment purposes.

a little extreme what about drunks, child molesters, and drug dealers

Any MHP dealer that you purchase your home through will get you started on the right track with subcontractors to set the home. 

Such charges, fees, and commissions are exclusive of and in addition to our fee, and we shall not receive any portion of these commissions, fees, and costs.7 Item 12 further describes the factors that we consider in selecting or recommending broker-dealers for Client’s transactions and determining the reasonableness of their compensation (e.g., commissions).We do not accept compensation for the sale of securities or other investment products including asset-based sales charges or service fees from the sale of mutual funds.

I would assume at that level you have to put in solid stone surfaces and low priced ones would be out of the question.With 50 plus units you should be able to broker a very good discount on a group buy of a large amount of slab stone, with 50 plus units that's going to be a large dollar amount and you'll find stone dealers very willing to put together a very competitive bid for you.

If you build and sell in under a year, you may be viewed as a dealer and be subject to shot term capital gains.  

If your primary role in a syndication is capital raising and you're not materially participating in the project you're an unlicensed broker-dealer. 

As an SEC Registered Rep, the deals I introduce investors to are very well-vetted, with great syndicators, as I work under a broker dealer, and we need to ensure that our opportunities are suitable for our clients' requirements.