This might not be a hack, but it is useful information.

“The reason that the rich were so rich, Vimes reasoned, was because they managed to spend less money.

Take boots, for example. He earned thirty-eight dollars a month plus allowances. A really good pair of leather boots cost fifty dollars. But an affordable pair of boots, which were sort of OK for a season or two and then leaked like hell when the cardboard gave out, cost about ten dollars. Those were the kind of boots Vimes always bought, and wore until the soles were so thin that he could tell where he was in Ankh-Morpork on a foggy night by the feel of the cobbles.

But the thing was that good boots lasted for years and years. A man who could afford fifty dollars had a pair of boots that'd still be keeping his feet dry in ten years' time, while the poor man who could only afford cheap boots would have spent a hundred dollars on boots in the same time and would still have wet feet.

This was the Captain Samuel Vimes 'Boots' theory of socioeconomic unfairness.”

Along these lines, I asked reddit last week for ideas of things that you can buy which will cost more upfront, but would eventually pay for themselves. My stipulation for the post was that they had to make the money back within one year, didn't require much more time or skill, and would have to be backed up with a calculation. YMMV based on your habits and climate, but here's what made the cut:

• Switching from disposable razors to safety razors
• Buying a weight set off craigslist and ditching a gym membership
• Buying a chest freezer off craigslist and buying meat only in bulk or when on sale
• Buying the tools for any home project rather than paying someone to fix it
• Buying a cable modem rather than renting it (or ditching cable and using a chromecast paired with internet services)
• Switching to a programmable thermostat
• Buying an electric mattress pad and turning the heat down 10deg in the winter
• Insulating your home
• Switching to a low-flow shower nozzle
• Keeping an herb garden/indoor plant rather than buying fresh herbs
• Using a menstrual cup rather than tampons
• Using cloth diapers rather than disposable ones
• Buying a washing machine rather than going to a laundrymat
• Buying a smartphone off-contract and getting a cheaper plan
• Using a breadmaker rather than buying store bread
• Homebrewing rather than buying beer (probably the most questionable ROI here because of the time and beer consumption needed)
• Buying a haircut kit and cutting your own hair
• Brewing your own coffee instead of buying it
• If you smoke, rolling your own cigarettes or switching to an e-cig

The meta life-hack here is to make personal questions engaging and use the internet to source ideas.