Our solar array is not mounted on our roof. They are on free-standing frames with the lines running underground to our house.
Currently, we have 30 panels (each one is 4'x5'), located about 120' away from the house. We are having 24 additional panels installed next week. The new panels are even more efficient than the current panels (which are less than 3 years old!). The cost for the original panels was around $29,000. The new installation will cost around $21,500. ALL our panels are USA-made (Sharp Corporation out of Memphis, TN).
We didn't want them on our roof because: the mounting would void the warranty on our roof; we'll need to replace our roof someday and they would all have to be removed to do so; they are much easier to maintain in their free-standing location; no worries about roof-climbing to clear snow off; no worries about wasps nesting between the panels and the roof (wasps LOVE those areas on roof mounts! With the free-standing, I can easily spray for wasps); and the cost was way less that roof-mounting. Though this is not a worry for us, should we ever have to move (there is no reason for that to ever happen), we could take our array with us.
I would talk to a reputable solar installer about how well those adhesive-type of solar panels will work for running a house.
As far as buying a couple panels to start, you need to make sure that future panels will integrate with existing connections to your house and to the other panels. Solar arrays are not necessarily one of those systems that you can mix-&-match brands, sizes, types, etc.
Really, talk to an experienced and well-respected installer about this!