Hi,
I would like to view files created by my home re-modeling architect/contractor and available in .dwg or .dxf format. My use is probably over the next year. What would be the software/license that I have to choose?
You need either SketchUp Pro or SketchUp Shop to to be able to import DWG or DXF files into SketchUp. Your profile says you are using SketchUp 2018. If that’s correct, you should be all set. If all you want to do is view those CAD files from you architect, maybe you could ask them to send you PDFs instead.
if viewing DWG/DXF documents only (i.e. no further processing), you may want use the free ODA Drawings Explorer for Win/Mac/Tux.
These should work just fine and free…
I Autocad has something called REVIEW? We did this for years with a builder we worked with. We could also LOCK our Cad files delivered to them so they couldn’t mess with them. They could mark them up for their purposes but couldn’t mess with the original file. Not sure what file type we sent but I’d guess it was DXF.
I don’t think they have REVIEW anymore but their 3 current products are in the link I provided above. One will even covert the DWG back to an older version, if one needs that 
converting back does the free ODA ‘Drawing Explorer’ one post above yours too and is a much less bloated application than the ADesk stuff.
Additionally, it uses the same DXF/DWG engine as SketchUp… because they do develop it.