The kind of camera you want to use for this kind of work, is completely up to you.
At this point, you may have a very good quality even with a high end smartphone, so good that in some side-by-side comparison with good D-SLR an non-expert eye couldn't tell the difference.
However, if you have to comply with some specs, this can help with a choice.
I would say, if you plan to sell prints up to 1m on the long edge, you may want to choose at least a 24mpx camera, regardless of sensor size. Given that you want something lightweight that will be easy to carry around, I would suggest something like a Fuji X100f.