What would I have to gain? What possible… possible… who… who
would… oh my god… HEHEHEHEHEHHH! …I have been waiting… I've been waiting all
day… waiting for Stalin to send one of his men to kill me… and it's you. Who do
you know who's ok with using purges, Jesse, who do you know who's allowed to
children to starve? Hmm?…

*Walt's car wash business

"The FBI, DEA and IRS doing a focused investigation into this are not going to be as gullible as Marie."

"Mr. White has manipulated me into thinking that Gus poisoned Brock, when actually Brock got accidentally poisoned by some plant!"

This is amazing to me that people are having this much trouble with Jesse's revelation about Walt poisoning Brock.  I really hope writers aren't reading these comments and deciding to do more Dexter-esque painfully explicit ghost dad exposition in the future instead.

The same reason Walt would need to work for Gus or get into the car washing business.  Hank would be coercing Walt into taking on the majority of the risk by manufacturing the meth, building Hector's explosive, and laundering profits through his car wash, while Hank would get the benefits of the laundered money.