Hi Congo and welcome to the Cooler.
For the most part, we recommend folks learn to do their own editing. Partly because there are some not-exactly-reputable people out there calling themselves editors who are more interested in separating you from your money than they are in whipping a ms into publishable shape. Even the well-meaning among them may not have the expertise required. It's also partly because if writers can't produce clean, grammatically-correct manuscripts, they're probably in the wrong business.
Minor issues with the occasional typo or incorrect tense will
not cost you a book contract. Every reputable publisher has editors on staff who will help whip your book into the best shape possible - for free - once it's accepted.
Why not submit a small portion of your work for the scrutiny of the good folks who haunt our
Share Your Work section? (The password is
vista.) You may find it doesn't require much help.
At the very least, don't be in a rush to fork over your money to someone calling themselves an editor or book doctor. Ask for testimonials from clients. Check to see if those clients have had books published (with other than self or subsidy publishers). Make sure you know exactly what to expect and how much it will cost.
Hang around here a while. Soak up the knowledge from the various forums.
Good luck.
PS - I'm going to port this over to the Basic Writing Questions board.