It's important to read your state law.

Conventional Manufactured 80% LTV/HCLTV/CLTVFHA VA USDA Manufactured.When a manufactured home has an accessory unit (mother in law, granny unit, guest house, etc...) the accessory unit will disqualify the manufactured home for financing.When a manufactured home is the accessory unit it will disqualify the property (technically Fannie / Freddie will allow, but investors do not).Very important -Accessory units are ONLY allowed/accepted, when the property is officially a "single family" property.

Thanks @Manon Sheiman , it's my father in law, and I'd make sure he'd be taken care of.

Each dwelling unit must have one main egress door, as well as each sleeping room, basement and habitable attic must have a means of emergency escape (door or egress window).Additionally, the code (IBC) for 3+ units is much, much more strict than the code for 1-2 unit buildings (IRC). 

I also own a law office with 6 employees.  

You'll want to check your local laws and attend a local realestate meet up...

Gary Davidson - Castle Law

do you think it mite be easier building a small granny in law suite with a desperate entrance?

me and my sweetheart have enough for the down payment on a duplex. we want to save to install a granny in law suite in the attic. just a studio unless the numbers make sense for more of course. from what I researched it can run me 32k to 65k on the cheaper side if I can use unused space.our goal with it is to build the studio then live in the studio while househacking and renting the large units then when we save up for the next duplex do the sameAnd just rent out the studio for 5 600 after wardsturning the propertys into suido triplexes.any problems I may run Into trying to do this?

Downsides are high property taxes, which cut into cash-flow, a lot of government oversight, ie...inspections, registrations, and tenant friendly laws.