Let's take a look at Owen Lars, shall we? Good old Uncle Owen, a nice old moisture farmer who raises his nephew and works the soil with nothing but his family and a few old droids. A kindly soul, one who doesn't want trouble and doesn't want to get involved in the wider affairs of the universe. The salt of the earth.
Except...well...admittedly, they never did delve too much into the economy of the 'Star Wars' universe, but doesn't it seem like a really stupid idea to farm for moisture on a desert planet with an extra sun? We know they've got interplanetary trade, because Han Solo runs cargo from one planet to another, so water could certainly be imported in quantity from a planet like Camino that's got it in abundance. Even if it isn't cost-effective to import water from another star system, there ought to be enough comets and similar water-bearing bodies that a space-faring civilization doesn't need to use condensation technology to get water.
And those droids...well, it's not like he's buying top-of-the-line equipment to help him with the harvest, is he? (Also, why is there a "harvest season"? Is there a monsoon period where water is easier to obtain?) In fact, he's buying stolen merchandise and is pretty comfortable with it. He doesn't even bat an eye when a bunch of strangers show up on his farm with merchandise that 'fell off a truck'. Perhaps that's not too surprising, given that he's within driving distance of the most notorious "hive of scum and villainy" in the galaxy. Good old Uncle Owen seems to be pretty sanguine about blatantly illegal activity in his backyard.
And would droids really be the best option? Sure, they don't need to be paid...but you have to buy them, service them, maintain them, and replace them (since as noted, it's not like Owen is buying quality merchandise). Hiring temporary labor just for the "harvest" seems like it would be a far more cost-effective model--but Owen doesn't seem to want anyone on his farm except Luke. In fact, he's also awful jumpy about Luke leaving the farm, especially when Luke mentions he wants to go to an Imperial flight academy. (Admittedly, Luke is planning on defecting to the Rebellion, but Owen may not know that.) Mind you, he's not nearly as jumpy about that as he is about a Jedi Knight taking interest in his farm.
So to sum up, Owen is living right next door to a group of crimelords, running a business whose model seems to be inherently and obviously flawed. He only works with close family members and robots, and doesn't like the idea of anyone in his family bringing the attention of current or former authorities onto his operations. It sounds pretty suspicious when you put it all together like that, doesn't it?
I'm going to go out on a limb here and suggest that Uncle Owen's moisture farm is a money laundering operation for the Hutts, a legitimate business whose operations serve as a front for the criminals of Tatooine to disburse their ill-gotten gains without attracting too much attention. Probably his paper business has a thriving workforce of dozens of people, from Boba Fett on down through to Greedo; even though none of them work a day on the farm, their tax records are scrupulously maintained. The farm probably shows a minor loss year in and year out, the sort of thing that you'd expect when you run a water farm in the middle of the desert. Not a huge loss, or tax agents might get suspicious (which is one of the reasons he only uses droids and family members), but not enough of a profit to get people interested in examining the books.
Keeping the staff down to family members and droids also avoids awkward questions, the kind of thing that leads to bodies being left in the desert for womp rats to eat. Given that, it's no surprise that Owen wants Luke to stay there, help out on the farm, and avoid any kind of involvement with the expansionist and bureaucratic Empire or the quixotic Jedi who Owen thankfully hasn't seen in years. Honestly, we only have circumstantial evidence to show that the murders at the Lars farm are the work of trigger-happy Stormtroopers and not, say, a couple of boys the Hutts sent round to deliver a message about what happens to people who don't do a good job of cooking the books.
That's how I want to remember Owen Lars. As a criminal conspirator in the Huttese crime families, eventually brought down by his own avarice a la 'Breaking Bad'. (And don't feel too sorry for Beru. She probably came up with the whole scam. Owen didn't seem smart enough to figure out all the angles on his own.) Luke doesn't know how lucky he was--if the Empire hadn't shown up, he'd probably have gotten some ricin in his next glass of blue milk for bringing Obi-Wan into things. Snitches get stitches, Luke!