If you are experienced, They will offer you a percentage on the billing rate. Normally it will be 80/20...
If you look at it, it looks cool and good, But catch is 1) You have to pay at the least 50% of H1B filing charges 2) You have to find the project and 3) You have to pay for the travel/accommodation expenses 4) You have to learn any new technology and above all 5) Even they split the 80/20 on Over time too.
So if you look at it, All they did was spent 1500 USD on you. Probably you might work with them for 6-8 years. Look at the profit which they get without adding any value to you or to the clients whom you will be working.