I would like to achieve top 3 position for the "yacht charter" in google.com. How long would it probably take and what annual link budget is required? Now I own 2 years old site about yacht charter with Google PR3. I will appreciate any ideas and rough calculations. Thanks!
A budget for linking building is dependent of how competitive your targeted keyword is. In your case your key word is "yacht charter, what regions do you or your client charter yachts in? Maybe you should aim for a more targeted keyword IE: "Miami Yacht Charter". If you go this route you'll achieve good results with a lot less efforts. I hope this helps.
"yacht charter" is a very competitive keyword. It gets 165,000 search volume per month. It's hard to say the exact amount you'll spend in optimizing your site for that keyword. My suggestion is to hire some linkbuilders from getafreelancer.com that suit your budget.