detached garage with one level in law suite

[lrusley]

We recently bought a house on 6 acres in northern British Columbia.  We are thinking of building a detached garage with a suite for my mom - in- law.  If anyone has any suggestions - we'd appreciate. 

Here are the challenges.  We have a lagoon that is grandfathered in.  If we add a bathroom, or kitchen, we would have to upgrade the lagoon.   What can we expect in installation costs, upkeep, and performance if we install a composting toilet and grey water disposal system?  We are on a shallow well, currenty that requires that we truck water in to top it up in the winter, which we are set up to do, so it's not that difficult,. but I don't think we want to go digging in there to attach a water line to the suite, - and water can be hit or miss here, so digging for another well is a risk I don't want to undertake.  So. A cistern that we bring water to would probably be her source of water.   Also, I haven't seen any plans that are similar to what we'd like - it would have to be a two bedroom, one level - main floor suite - maybe behind the garage area?  Ideally it would be a 3 or 4 car garage,..with one car area for her,...I am thinking if she drives up directly to her door, it would reduce the need for us to shovel snow off her entrance.    

I would love to hear if anyone has seen something similar, or has advice,....I have been lurking here at country plans for quite a while - we were planning on building a simple little house on land before we stumbled across our current place,..it was love at first sight ,..
thanks in advance -  I love how everyone has a can do - problem solver attitude here,-
By the way, we don't necessarily have to build a garage - we are doing fine without one right now - our current feeling is that if we are building something anyways,.it might be just as well to add the garage area,... but if it's significantly more expensive to do that, then we don't want to.