You can always trust writers under companies like uvocorp and writerbay.

Turnit In is very effective, though a student must submit his/her paper, however, writers should not use the software.

Grammarly is very effective, both for students and writers.

Buying accounts is very risky, unless you are a really good writer. If you are not, I am strongly advising that you don't buy, unless you want to lose your money.