How much should be the return on investment (in landscape design or construction field - at least 3-5 years.) to be successful?

3 times to the invested money

I think so. At the University of Economics in the industry we studied pricing activities landscaping, can be summarized in: materials + labor =%%.

Of course, that other items, such as transport, mechanization, storage, and other unforeseen costs are relative to individual cases and added to the sum%!

In the practice, however, are incl. more as:

% taxes, guarantee, reserves at difficulties in payments/ inside investments and others.