Commercial rating?

So if I had a float plane and wanted to offer to fly people and stuff out
to lake bound cottages, I'd need to set myself up as a Part 135 operation?

Yes, you would have to be 135 to charge people to fly them places.
You'd also have to be married to an insurance company CEO.

How about my previous question about doing photography?

Photography is fine. You can be paid to take pictures as a commercial
pilot. In fact, our Sacramento FSDO has said that private pilots may be
paid to take pictures themselves as long as they are working directly
for the end customer (i.e. not employed by an aerial survey company). I
think the FSDO is wrong on that but they are the ones to enforce
anything. You can also tow banners etc. In reality, those jobs are not
plentiful though.

-Robert