If you don't have a permit, fruit picking or harvesting is probably one of the easiest ways to make extra cash. Employers usually turn a blind eye to the law and pay up front. This sort of work is available almost everywhere. The best way to get a job is to approach farmers directly or ask around the nearest village. However, timing is very important. If you are too early or too late in the harvest season, there will be no work. If you show up in the middle of the harvest, all of the jobs might be taken.
You can also earn extra money by publishing articles or photos of the places you visited. Travel photography can be very competitive, so prepare to take a hundred shots before some get accepted. Many magazines and newspapers also accept travel articles based on the pictures that go along with them. Make sure to use a professional approach when writing, as simple essays are almost never bought. Also make sure you write with interest and depth, with the occasional offbeat angle to make your article marketable.