I would save the $100 each month as free adverts are the best! Here is list of free suggestions:
Tell your friends: I'm sure you can think of a few friends who would be prepared to join you on this venture. Send them a link to your OWN sales page and explain in person all about the system. Let's aim to get 1 friend to join you.
Facebook / Myspace: If you use one of these you have access to 100s of people. Make a bulletin or post about your new website. Facebook will also let you make fan pages for websites. So you can become a fan of your own site and ask your friends to become a fan. This is the clever bit! When they become a fan it's listed on their updates and all their friends will see your page. Again, let's aim to get 1 person to join from Facebook or Myspace activity.
Video websites: Youtube and other videos sites are a great place to promote your site. Make a short video telling people about your site and how they could join you. Remember to show your website link in the video. Don't just use Youtube. When you have your video you can upload it to many video sites like, veoh, metacafe, dailymotion etc. Let's aim to get 2 people to join from video promotion.
Free websites: There are lots of companies that offer free websites. All you need to do is either write your sales message again or use the advert space to link to your own sales page. It may take a bit of time for these to work their way into Google™ so let's assume we will get 1 person to join from here within the first 30 days. Here are 5 system that provide free sites:
www.pseudotube.com - free video site
www.squidoo.com - free article site
www.blogger.com - free blog site
www.synthasite.com - free general site
www.glogster.com - free poster site
Email signatures: If you use email every day then make sure you list your website in your signature file. This way every email you send will have your information. If your friends send you joke emails make sure you forward them to everyone you know with your signature included. You will be amazed how far some of these emails spread. Expect to get another 1 person to join from this.
Other webmasters: Make contact with small to medium sized websites. Tell the webmaster about your site. Most sites will have large mailing lists. If you can get the webmaster to sign up and then send a message to a few 1000 people you will have a great second level commission. Work on getting 2 people to join via this method.
Forums: Some forums will allow you to have a link to your website in your signature file. This is a great way to get people to see your site. You should only do this on forums that allow links as spamming messages is not suggested. Find some of the biggest forums and get involved. Aim to generate 1 person to join from forum activity.
Social bookmarks: There are only two sites you need to work with. Post a story about your site on digg.com and stumbleupon.com. This will generate you 100s of visitors within a few hours. This traffic soon dries up but it should get you 1 more person to join.