Hell, a good start to dealing with part of the source so far as that particular border goes would be decriminalizing or legalizing pot, maybe some other stuff, cut some of the major problems driving people away directly and otherwise off from a metric fuckton or two of revenue. Throw in muzzling arms sales going south of the border and giving our own shit enough teeth to stop some of the less direct stuff filtering off in that direction, and you've just made several orders of magnitude more progress in reducing incentives to cross the border than a goddamn wall can. Extra bonus points, any of those could function as an actual revenue stream via taxation and criminal/civil penalties for firearm trafficking violations.
Just think of it. Ways to reduce immigration, assuming that's a goal worth a damn to begin with, that not only could manage to be a fiscal net positive, it could engender good will with other countries and help progress other nations -- some of them close neighbors and excellent possibilities for strong relations -- and their populaces towards a better, safer, tomorrow.
Instead, of course, we get promised a fucking wall. Damn thing's probably not even good in bed.