I have a macbook pro 15 inch 2010 and I spilled water on it when I try to turn it on with the charger plugged in it makes a chime but blank screen. What is the cheapest way or service to fix it I can not afford a new mac.
Unfortunately, if the liquid had time to spread enough, just about everything can be damaged, and therefore if you plan on having it serviced (assuming Apple) - it will cost quite a bit to be brought back up to working condition. You can go and receive a quote to be sure, but it may end up costing you quite a bit, at which point it will make you think you may as well get a new laptop. I realize you said you can not afford it, but unfortunately this is likely to happen.
It depends on the severity of it though. You can use some typical household tricks like the good ol' bag of rice, but that only has reported success immediately after the liquid had been spilled. In all likeliness if you had tried operating it, etc since then - standard household "tricks" are likely to fail, but may be worth a shot anyway.
Other than that, I agree with the poster above to take a look at an iFixIt teardown or hunt online (YouTube for video guides) for how to properly try to remedy water damaged parts without replacing them. I don't know if you will have much luck but if you can't have it serviced then you don't have much of a choice.