Unfortunately, if a house foundation is not "maintained" and if you have heavey shrubery and trees, you are likely to have foundation problems. If your house has been repaired, find out who the contractor was and what the guarantee is. Most reputable foundation contractors will provide a guarantee of some sort. It is also quite likely that a structural engineer may have been involved in the repair process and would have provided a diagram to the contractor and home owner showing pier locations.
Don't necessarily be afraid of a house that has been repaired. You can always have an engineer look at it if you are uncertain.
Also, DO start a maintenance program of the foundation. This means using a soaker hose (available at a home improvement store). My husband and I are in the foundation repair business in Dallas. We are constantly amazed when don't "water" their foundation. This is a major investment. Take care of it. I have a soaker hose around my house with a timer and water weekly during the winter and then during hot weather (with no rain) I run it 20 min. every 8 hours. My water bill is high in the summer but I don't have foundation problems.