I've been doing media buy for the last 3 years. Mostly pop traffic, but also some push, some native, and some Facebook. I've managed 7 figures of ad spend.
Finding winning campaigns can be expensive and time consuming.
You better get ready to lose 20-30k$ to get started (I disagree with guys who said you need 1-2k$ to start).
You don't need to strictly have that amount sitting in the bank upfront because you will spend progressively, but if you plan to test the waters with less than that and stop if you don't succeed, you will most likely run out of money before you find anything promising
And it's not so easy to think "I'll just spend 100$/day over a month, so I just need 3k$ for month 1". Because you will get into situations that look promising and you will want to increase your ad spend testing rapidly other traffic sources that might yield a better ROI or volume, etc., just to realize that suddenly you spent 500$ in a couple days without success. Media buy is about being able to scale FAST and HARD something that works. So you need to be disciplined with the budget but also you need to be open to aggressively bump the spend for potentially nothing.
In my beginnings, I burnt 15,000$ over 6 weeks or so. Then when there was 1k$ left in the budget, some campaign started showing promising results and I was able to scale it to 500-1000$/day.
ROI of that first campaign was 100%, but you are constantly reinvesting a lot of it into finding new winning combinations in new geos and traffic sources, VAs, etc. And it's very hands on.
On top of that, tools are expensive. You will need a good cloaker, and the good commercial ones start at 300$+/month. If you plan on cracking some of the "premium" traffic sources get ready to play cat and mouse games with multiaccounting and multi VPS setups, depending on the vertical and how aggressive your marketing is. Tracking platforms and tools that can help you optimizing campaigns programmatically are pricey, etc.
BHW seems great for learning a bunch of different things, mostly related to ranking stuff, which is what almost everyone who gets interested on making money online will try first, due to being much less demanding on the budget side. In general media buyers hang out in other forums.