Great option for residential and mixed-use real estate investors! 

With the duplex, you can do both rental options.  

Quote from @Jimmy Chao: I am weighing some options to help my younger brother buying his first primary with a fixer.

Obviously the numbers and location would determine which is the best option for me but these would be my preferred methods. 

If they don't pay willingly, what are my options? 

@Cole Starin sometimes it makes sense to sell the WORST property in your portfolio.Another option is why do a LOC on the duplex, when you could just do a $100k cashout refi to pay off all your debt AND keep the property?

Believe it or not, these things actually impact all parts of the housing market, not just the new home sector.Again, to truly weigh the options in front of you, I would suggest having a Realtor do an evaluation for you, and give you a pro/con rundown of each option. 

If this property is hard to rent, or is functionally obsolescent (only 1 bathroom, no yard, etc), or has deferred maintenance that will be costly, or is in a location that is not appealing to Tenants, then maybe a sale would be a good option in favor of a property that has better Tenant appeal, which will likely increase rent and avoid long vacancies in between Tenants.An option to consider....

But I would remain open to long-term rental as an option as this seems like a more stable option in terms of income, again this may be my inexperience talking.However, I have always  been somewhat risk averse and investing in real estate is always a big venture, in my opinion/experience, in terms of capital.

Being a NYC resident (originally from Long Island), the price of entry in the area is on the higher end, so I've been considering some options in the NY Capitol region, as well as NJ and CT.