Percentage of sports bettors who win

[VegasRunner]

This is a pretty basic question.

Anyone can get lucky pick five out of five winners on any given week, but in the long run (years), how many people are actually seeing a profit by betting on sports?

The reason I ask is this:

I live in Vegas and I have a brother who lives back east. He likes betting football, but with all the problems of online sportsbetting, he's decided that it's easiest just to place his bets through me. He calls and ask me to place about 5 bets (average $100) a week for him.

I'm wondering if i'd be better off simply not placing his bets and taking the action myself. (Why does Ceasar's Palace deserse that vig more than me?) My brother seems to spend a fair amount of time reading up on the games online, but even so, I don't think he's too likely be able to beat Vegas.

Assuming I can stand about $5000 in variance, I'm probably better off taking the action myself, right? Not too many people are beating Vegas, right?

Subquestion: Assuming I will pay his winnings out of my own pocket, is it morally reprehensible to not let my brother know that I'm not placing his bets in a casino?