Bet-Funds is a HYIP that makes money from sports arbitrage – a situation that occurs when bookmakers’ prices differ enough such that it is profitable to intelligently purchase all outcomes.
Some past arbitrage can be viewed in their site.

This program offers four types of plans. All of which lasts for one year. With the exception of compounding plans, interest can be withdrawn every week.

BFS ($5 - $999) – weekly interest of 5%
BFM ($1000 - $4999) – weekly interest of 5.5%
BFP ($5000 or above) – weekly interest of 6%
BFC ($5 or above) – 6% compounded weekly

Bet-Funds Website Information
Website Title: Bet Funds- Arb bets mutual fund

Bet-Funds Server Data
IP Address: 200.46.204.163
IP Location: Panama – Panama City – Hub.org
Response Code: 200
Blacklist Status: Clear
SSL Cert: www.bet-funds.com expires in 212 days.

Bet-Funds Whois Record
Registered through: GoDaddy.com, Inc. (http://www.godaddy.com)
Domain Name: BET-FUNDS.COM
Created on: 11-Sep-06
Expires on: 11-Sep-07

Domain servers in listed order:
NS.EARTHTECINC.COM
NS2.EARTHTECINC.COM
NS3.EARTHTECINC.COM

Interview with Bet-funds
Q: Why I can only choose the compounding percent to be 100% in the compounding plan?
A: The compounding plan is compounded weekly and is only set to 100% as it is for those seeking capital growth in the long term, if you are looking for steady income then you should choose the regular plan where you are paid weekly.

Q: Your domain name will expire in Sep 2007, only two months after today. Does this mean that I can only get back the profit made within these two months?
A: Our domain name was registered by our webmaster and it will be automatically renewed before expiration.

Another interview can be found here

In my opinion, the rates are quite stable. And the admin is quite active in forums. So I think the site will not vanish in the short term.

Good Luck.