I cannot stress this part enough, but get the breaktru calculator and play around with it some. Make sure you understand each and every field you are inputting data into. Once you figure this thing out, mixing juice becomes very easy.
As to the cost, figure it like this. You WILL have some upstart costs just like you did when you first started vaping and you bought your hardware, kits, cleaning supplies, etc. But after a few weeks or months, the costs are recouped as you are saving money. My wife was vaping a very simple peach juice from a vendor for about $16 per 60ml bottle, plus shipping. With DIY I'm able to make her that same bottle for about $3.50, no shipping. I do use the higher concentration nic (100 mg). If you are going to use that, please make sure you wear gloves and cut the nic base immediately. I cut it down to 25mg the day i receive it and then work from there. The only dangerous part is the cutting and i do that very carefully.