I know people making $20k+ months couch flipping and investing in vending machines.

This is pretty low hanging fruit: If you do not already own real estate (personal occupancy) I would start by purchasing a SFH or 1-4 unit using a conventional mortgage:1.

We also have an ice machine in a beach market to make sure the cooler is always ready.  

I would feel safe using the security deposit on smoke mitigation on turnover which might include kill/paint purchase of ozone machine steam cleaning or replacing carpet etc. remember to account for useful life if replacing.

I do know I have built a strong relationship with him over the years and in many ways it’s starting to bear extra fruit!

Where I'm stuck is whether I should use a metering system that pre-prints a stamp onto the envelop or find a machine that can place a physical stamp onto an envelope (obviously I can't sit there all day stamping).I'm thinking from the perspective of mail that looks to "businessy" vs. mail that looks more personalized for better response/conversion rates.

FX, Crypto, Flipping Houses, Sub2, Gold and Silver, Rare Earth Metals, Day Trading, Bernie Madoff, Vending Machines, Car Washes, Amway, any MLM.....whatever the dream of the day is.In all of them, you can make money, you can get rich, but almost always it takes a lot of hard work, blood, sweat, tears, missed holidays, working on weekends, money, risk, stress.

Best wishes i looked at the 3d printing  the machines are really expensive and the logistics can be pretty tough .. will not work well in super tight building lots or areas you need space for the machine and the big pile of sand :)  but on large lots and small acreage.. and the machine was I think 600 to 800k .. but then you own it..  

That is where I met some of my most fruitful partners, contractors, mentors, and lenders... at these very meetups.

This real estate investing is not a race its a journey and it will take time to see any fruits of your labor.