Good domain names could have less than 1,000 searches, and sometimes even no searches. The domain name’s value really depends a number of factors, including the market value, past sales, demand and your brand.
If the .com or .com.au domain name is not available the next best thing for an internationally targeted domain name is a .net.
.biz domains do not hold as much trust with users as .com and .net and hence these are sometimes seen as SPAM or a less important website. However it is a good option to purchase a few of the popular domain extensions for your domain to ensure other business do not register the same domain as you with a different TLD.