Hi, the question is in topic. I'd like to estimate if domain would be ok for me, can I do that somewhere or I have to pay no matter what?
Yes, you can check out the following company: domainsforlet.com or leasethis.com. Let me know if you need more help finding the perfect domain name. Thanks, LexisDomains.com
Many, or most!?, major domain registrars offer a few days grace period during which you may cancel the domain and have the money be refunded to you.
Domain tasting is no longer free though. I'm surprised you guys didn't know this. Anyways, you can "taste" a domain for 5 days and get a refund. But it will cost you about 3 cents every time you do it. But yeah, if 3 cents isn't a problem then go ahead.
you can get one year free domain in register.com (I think) You can try there for one year as test period.
Some of the country domains can be pricey but generally domains are pretty cheap to buy. If your business plan stacks up then surely buying a few domains isn't going to be a problem?