Building additional Master Bed/Bath as room rental

[Jose Saladin]

As part of my strategy, I would like to build an master bath/bed extension, with its own entrance, to the three bedroom, two bath home mentioned in a different post.

A 20'x15' (could be smaller) structure that can accomodate the bedroom and the bathroom. Maybe even allow for a small kitchenette for full privacy, although it would be attached to the house with a connecting door.

The yard has enough room to allow for it. While it would take up half the yard, with proper lanscaping, it can be made into a nice looking haven for the tenants if they choose to use it.

Could rent out for $1k in the area. My thinking is increased value and cashflow on a long term hold. Not immediate returns.

Any thoughts on this?

Build cost? 

Tax implications?

Any other thing I may not see?