Yes it ok if you don't buy a domain name . But if you see you stsrt making money it's a good idea if buy a domain .
2 weeks is enough to see if its profitable but that depends on your way of driving traffic .
If your doing seo then you need to buy a domain and buy a membership for alot longer.
If your doing fb ads , no domain is fine , 2 weeks is enough to see if its profitable .
Also if your reaching the end of your trial, and your on the edge and not sure, talk to their customer service and they may extend the time