Also open to different type of rentals: I'm thinking co-housing/co-living can be a nice way to increase returns, so will be looking in Belgian regulation for this as well.. 

Unfortunately, as you probably have found out, the rules and regulations are not necessarily clear on owner occupancy. 

You must analyze all the data (size of properties, # of properties of each size, location of best producers, regulations, # building permits for that size issued in the last year)3.

Limited partner's test: (Only three test -Under temporary regulations, individuals who are limited partners and meet the more-than-500-hour test, the five-of-10-years test, or the three-year lookback test are treated as materially participating in any activity of the limited partnership for purposes of applying the passive activity rules)De Minimis RuleIf a qualifying real estate professional aggregates activities into a single rental real estate activity and the taxpayer’s share of gross rental income from all of the taxpayer’s limited partnership interests in rental real estate is less than 10% of the taxpayer’s share of gross rental income from all of the taxpayer’s interests in rental real estate for the tax year, a de minimis exception applies—the taxpayer can determine material participation under any of the tests in Reg. § 1.469-5T(a)  that apply to the rental real estate activities.

Low taxes and regulations. 

I'm and experienced STR owner and manager and multifamily owner operator, so I know about 28 day minimums, local regulations, underwriting, insurance etc.

Are you familiar with the anti-kickback provision of Section 8 of the Real Estate Settlement Procedures Act (RESPA)? 

Hi @Megan Fitzgerald I would be sure to do your research online and it may be worth checking with a local real estate attorney as well or another local attorney who may be familiar with the your areas laws/regulations.

Knowing the rental increase in California is regulated, I am not intending on raising the rent for at least a year if at all. 

There's rent control, rent increases, rent regulations, etc.