I will save money in the long run, right?
You will save a TON of money
IF, IF, IF you exercise self control when buying flavors.
Here are the economics... after you get your feet wet, you can buy VG and PG for about $25/gallon, shipped. That is 1.3 cents/ml.
Nic is about $50/liter in 100mg concentrate. If you vape 10mg nic, that would make 10 liters and works out to 0.5 cents per ml of final juice. Contrary to what you might have been told, nic is really cheap in the dilutions you use it, if you buy it right. You may not be comfortable handling 100mg nic right away, you might get your feet wet with 24mg concentrate or something like that, in a strength you may be used to actually vaping. Or whatever you are comfortable with.
I vape 3mg max now, in a dripper or subohm tank, so my nic cost is 0.15 cents/ml.
ETA: assuming I vape 15ml a day, at 3mg that $50 liter of nic will last me 6 years. That's about as cheap as things get.
You can make unflavored juice for under 2 cents per ml, that's less than $0.60/ounce (30ml).
Most people can buy a minimum year supply of unflavored juice for $75/$100. Add $50 for supplies if you don't go too crazy building your chemistry set

. Some syringes, a starter set of juice bottles (they cost more than the juice!).
Now you get to flavors. The basic cost of flavoring is about $6-$10/4 oz bottle for TFA flavoring, direct from TFA/TPA or some vape shop distributors. So the theoretical cost is about 6.7 cents/ml, and if you use a very high flavor mix (HFM) like me- 30%, that averages out to about 2 cents per ml of final juice.
So your theoretical cost for a high flavor mix juice can easily be around 3.5 cents/ml, or about a buck for a 30 ml/1 oz bottle that would sell for $10 - $30 as a commercial mix. And you may well find your juice (especially at the HFM ratio I mentioned) to be fully premium or better than anything you buy.
Now obviously if you buy 100 bottles, 4 oz each, you are going to spend upwards of $1K. So you will probably do something like the 8ml sample sizes from Wizard Labs at $1.49 (18.6 cents/ml or triple the bulk cost). And then probably buy 1 or 4 oz bottles of your favorite flavors. And interestingly, the basic cost of flavoring for a 1 oz bottle is $4 - $5.50 or so, where TFA 4 oz bottles will run you $6 - $10 depending on flavor and maybe averaging $8.50 or so. So what do you think you end up buying?
(TFA is not only a very wide line of flavors, with a ton of recipes here, but it is probably about the most economical flavor line. From a cost and flexibility standpoint it is hard to beat although other lines have their advocates)
So, the short story is that I am making flavored juice now for 3.5 cents per ml but I've spend $603 just on flavors in the 9 months or so since I started DIY. LOL. But I had a fun time doing it. And while I was mixing it kept me out of the bars (I never mix at night, that's bar time!)
Don't be me... don't get excited about every recipe you see and buy 100++ flavors. Unless you want to

. There are actually some good lists of basic flavors, where if you like fruity.sweet flavors you can be well covered with about 20 flavors.