Only users who know the login and password can access private proxies for Google. That's why no one will be able to compromise the bought IPs. The administration will not impose sanctions, as it won't be able to detect suspicious activities. Individual proxy servers are much more stable and faster than public ones.
Free proxies are promptly included in black lists of large websites or don't work at all. That is why they cannot provide high quality, when you need to do mass actions. Proxies you pay for are not blocked, and are validated by service providers. That's why chances to face defective or banned address go to zero.
You can buy affordable individual proxy servers for Google at Proxy.Market. Stable and fast IPv4 and IPv6 proxies of HTTPS and SOCKS5 protocols are available. Each of them is validated before delivery, so all bought addresses will operate efficiently and cope with the set tasks. And 24/7 technical support will help resolve any issues, and set up the bought proxies correctly.