Day 4
Subject: Get this part wrong, [firstname], and you're doomed to failure.

Hi [firstname],

Today I want to talk about the most important decision you'll make regarding your membership site: The niche you're going to operate in.

The truth is, some niches are just more popular than others.  You'll need to find a niche where you can identify a need, and where people are prepared to spend money to get a solution. Plus, you need to find topics where demand is high, but the competition is low.

This is true of any website or product, but is even more pressing when you're starting a membership site as you need to keep meeting that need over and over again.

Some popular niches for conventional membership sites are:

Hobbies
Health
Business related.

For unconventional membership site types, try thinking outside the box.  If you can think of a recurring want or need that can be satisfied online on an ongoing basis, you might just have the next  Facebook or Dropbox on your hands!

A few tools to help 

I find the following tools help me a lot when I'm doing niche research for membership sites:

Google Adwords Keyword Planner
http://adwords.google.com/KeywordPlanner 
A free to use tool.  Sign in with your Google ID

Market Samurai
http://www.marketsamurai.com/ 
An excellent tool (once you get your head round how it works) that can provide a TON of data.  Paid solution, but with a free trial.
  
CB Engine
http://cbengine.com/ 
Find out what's hot on ClickBank right now.  Also a great example of a curated data membership site that operates on a freemium business model.

One thing to note, though 

If this is your first membership site, it's best to avoid the Internet Marketing/Make Money Online/Work from Home niches unless you have a LOT of experience in these areas.  These are VERY overcrowded and competitive. If you're a newbie, you're pretty much setting yourself up to fail if you go after one of these.

Warmly,

[Your Name]
PS. Don't forget to grab your copy of my guide to starting a membership site.  Here's the link [link to sales page].