No such thing as a 'hobby' business - it's either one or the other. If you have the slightest intention of approaching with anything less than 100% professionalism, you're going to end up as an accident statistic. It's a difficult and dangerous way to spend your time in the air, more so when it is single pilot (I wish the CAA would outlaw that practice), and the less 'cowboy' operators there are the better. There are curently too many gash operations which give the entire photography/survey business a bad reputation because of their halfwit antics clowning around at minimum level, busting controlled airspace and producing shoddy, over-priced results.
If you want to do it, do it properly, and stop trying to cut corners and get it done on the cheap. Otherwise you're liable to find out the hard way whether or not your great idea is legal or not.