He can't apply for citizenship directly. He must become a permanent resident first. Once he has been a permanent resident for a number of years and lived in Canada for several years - he will qualify to apply for citizenship.
The Federal investor program was closed some time ago and new applications are not being accepted.
Your friend will have to look into the Provincial Nominee programs to see if he qualifies to apply under one of these programs. Each program has different rules so he will have to read up on each to see what it takes to qualify. To apply as an investor through the province of Ontario, for example, you need to be able to invest a minimum of $3 million dollars.
http://www.cic.gc.ca/english/immigrate/provincial/apply-who.asp