[RealJames]

Hosting for men and women is quite different. Here are things that they have in common though.
I'll give information based on what I've seen in my friends who have done it.

It is a gateway into the sex industry, not slowly, and not smoothly.
It's an easy way to alienate your real friends and end up very lonely.
(Japanese people, more so than most, care about who they associate with.)
Your "friendships" become very artificial.

It's a sad life, in the long run.
If you think you have what it takes to do it, and get out of it before things go sour, you are special.
It's demoralizing and degrading, which breaks willpower and most can't escape the lifestyle.

The reasons mentioned before regarding visas, your home, etc are all very good points too!