Mining

There are LA owners who hire people for advertising, hosting events on their lands, even to FAP on their lands. There are people sometimes looking for human amps, as in someone who shoots with them, they get all the loot but give you your decay+ammo back or provide the weapon and ammo for you. However, this does require you to build up a good reputation ingame or sometimes requires you to come into contact with the right people. It takes a lot more effort then trading, but at least once you get the ball rolling, it still feels as a game.

I assume you are talking about the SSI's there. Usually you only get paid your decay there if you are a helper there. However, healing for decay at SSI's is the first step into the organisation, if you function well with the team and know what you are doing there is usually a step up to hosting events as well which does pay some PED ranging from 2-5PED per event.
Healing for decay for hunters from what I hear depends on how good you heal and what skills you got. A smalltime healer usually only gets paid for decay unless the hunter gets an insane amount of globals and is very happy. Once you get up to I believe somewhere around lvl 15-16 paramedic (when you max out an SI Heart at least), hunters tend to tip a bit more often, ranging from 2-3% healer loot or just pure PED like 1-5PED on top of your decay.

Given that there is quite some competition in the transport business (from what I see at quarry on arkadia) I'd say it would take a while to really make profit on it and even then the margins would be rather small.

But correct me if I'm wrong, it's only an outsider's look on the matter...

Depends on the transport service. A privateer or Mothership transport service is a really tough business atm, because you got already a few people having a steady schedule they warp people at with reduced fees. Outside you might have had a chance but that is mostly taken by Equus. However.... realistically in  this thread we arent talking about a warp transport business :P because I dont believe many of us are that big of investors :P.
Realistically you are talking about a taxi service I guess correct? Those DO run, compitition is pretty brutal but if done correctly you can have 2-3PED profit per taxi run (including MU on serveral things). This does mean you cant transport people with lootables.