Exactly. It's a hobby that pays for itself, and allows us to justify the cost to your spouse or significant other. For myself, when I used to do this back in the mid 2000's it was actually to supplement my income. However, now I have a well paying job, and it's primarily to justify me buying these several hundred dollar lego sets, as it is a bit of a splurge.
If you truly need to make significant cash from Lego's it becomes a full time job. The amount of time spent tracking sales, market research, listing, packing, shipping, dealing with returns and customer complaints, etc. starts to consume a massive amount of time. If you have a family and a full time job, it just becomes unfeasible to make more than a couple thousand a month at most with the time investment required, which brings us to which certain investment strategy is best for your lifestyle.
For me, the long term hold on the pricey sets is by far the best return for my time, and I suspect it is for any body who does not have the time to churn through packing and shipping 10-15 sets a day for a 10 dollar profit. As you get older, money is no longer your most valuable asset. Time is. Time is money. And spending a couple hours packing and shipping to make a 150 dollar profit is not worth it for most people in this game. With a long term hold you can make potentially 200-300 dollars in a sell and the time it took is the same to pack and sell for a 10 dollar flip. These are vague estimates. Your actual time may vary, but I tried to round to make math easier.
5 min. to buy the item (seconds with amazon 1-click)
5 min. to pick up item from doorstep and store in basement, storage unit in home, etc.,
20 min. for market research and to list on ebay, amazon, brick link when it comes time to sell.
10 min. Answer a couple emails on product
30 min. Pack and ship product 30 min.(includes time to put on label, and drive to post office and ship, shipping from home reduces this)
70 total minutes to buy an item and send it out. 200-300 dollars for an approximate hour of someone's time is much more appealing than 10-15 dollars for the same time span for someone that has a full time job, spouse, kids, etc. on top of legovesting. The short term hold yields the same amount "work" time, however, your profit is much lower for the same amount of actual "work." Your dollar per hour wage is that of a fast food worker. If the flip is 30 dollars/hour you've at least moved into a realm of a more respectable "wage." I've done fast food in my youth and college, and I can say I am glad I am past that point.
Another obstacle toward the short term flip and an obstacle for anyone with an income is taxes. If you are paying 25-35% on your tax return, suddenly, that 10 dollar profit is reduced to 7.50-6.50. Now we are sub minimum wage. At least a medium term hold would make it worth the effort at that point. Again, this all depends on your tax situation.
This is all dependent on if you have the capital to tie up thousands of dollars in Legos for long term. Obviously if you are buying on margin the Long Term hold might not be the best for you.
The ideal goal is to have a continual stream of old "mature" stock that you can sell for the 200/hour wage, so you are constantly making a good wage. I managed to achieve this in 2007, but sadly had to shut the biz down due to life changes, and am only getting it restarted. It is my goal to build up a nice portfolio so when I retire I can do this as a retirement gig, when income and therefore taxes are lower. It will also keep myself from being bored in the retirement years.
The stock market, while risky, and basically gambling, is highly appealing to many because it takes SECONDS to buy and sell stocks. Your per hour wage can be astronomical. Sadly, stocks are incredibly risky, but with great risk there is potential for great reward.
Either way, there are many strategies, you just need to pick the one that works best for your lifestyle, life goals, and how much you believe your time to be worth.
I apologize if that was off topic. Mods please move to whatever forum you believe this to relevant.