Erosion & Drainage Problems

I am currently looking at a home I would like to purchase that is around 10 years old. It sits on a sloping site. On both sides of the home there is substantial erosion, and I can see where they have tried to install french drains around the property. The owner said he had planned on adding retaining walls, but did not get around to it, but doesn't fell it is a real problem. This problem is mainly around the baasement, but goes along both sides of the house and in several parts of the yard (3 1/2 acres).

My concern is the major erosion, drainage problems, possible moisture in the basement and leveling of the yard for maintenance and what steps I should take next in determining how much it would costs for the repairs prior to making an offer. Are there any "experts" in this field I can turn to outside a normal appraisal without getting sales pitches just to get a true assessment. Any advice?