I've taken a look at Godaddy & Namecheap.
It seems that Godaddy offers $1/domain, but when renewal comes, won't they bump it up to like $10?
Domain Name Registration, Domain Transfers. Your domain name search starts here.
Namecheap seems to offer $3 for first year.
Namecheap.com - Domain Registration Pricing
Which one's better for proxies? And is it worth renewing these .info domains?
You can get .infos from godaddy even cheaper if you buy in bulk (more than 6). I do that and usually try to sell them before the next renewal date.
I see. Where do you sell the sites? Digitalpoint,...?
I prefer NameCheap because they are extremely helpful and I trust them a million times more than GoDaddy. On top of that, while .info may cost you $2 more with NameCheap, you also get WHOIS Privacy and an SSL Certificate included for free.