You think an ink-refilling is still a viable business?

Yes it is very good business. If you ask me the best place (location) to open "ink refilling" is near to educational institutes, like colleges, muiltnational companies. My friend is in refilling business & he is making very good profits. I live in Bangalore, INDIA.

There are a lot of businesses like that here in Honduras. To be really competitive there are two tricks (maybe you already know these tricks, but I'll put them here in case you hadn't thought of them). First, do delivery if possible. Then people just have to call your number and say, "I need some ink" and you send it over with a courrier or on a motorcycle. Second, have your inventory of ink cartridges, and then people bring in their empties, but you don't have to fill them on the spot, you just hand over the filled ones and take their empties. This is how you can do delivery, you bring them the fresh cartridges and they hand over their empties. Good luck with your project