Avoid being vague If you have references include them. Dont say available upon request. If you have gaps in employment explain them clearly. They will probably come up in the interview anyways. Being prepared in advance by giving complete information in your resume is better than being caught off guard in the interview or worse skipped over all together.
Your resume is your marketing tool for success. You need to be able to advertise your skills and ability to succeed with your prospective employer. The format and feel of your resume can either open doors or close them often this feeling can make people question why they didnt get the interview or thinking they are not qualified.
The cost is too good to be true. It is only human to try to find the best service at an affordable price. However it is also true that you get what you pay for. If a service says that it can write your resume for a few dollars it is better to be cautious. Creating good quality resumes requires using specific skills. The cost can be lower only if the summary of your career is part of a mass produced set of similar documents.