This question is tough to answer because there is no answer. Every single case will be different, and no two situations are the same. The reason is that Google doesn't even know. There are absolutely no guarantees when it comes to Google's organic search results. We can tell you some general ideas based on the actual results we have witnessed in the last nine years ranking contractor websites.
First off the reality is that you will need a minimum of 3-6 months to see any significant movement. The general rule of thumb, though is 6-12 months to see real results. The customers who beat their competition every time, though are the ones who stay consistent for over a year and continue their campaigns ongoing. We have had customers with us for nine years and many who are 2 + years. These customers by far beat out their competitors, and since they never gave up, they have much stronger domain authority with Google.
THINGS TO CONSIDER
New Websites Have To Start In The Very Back
Websites Who Are Page 2-5 Will Move Quicker
It Takes Google Roughly 1-3 Months To Recognize New Backlinks
If You Stop SEO, Your Competition Won't
If Your Not Doing SEO Then Don't Expect Top Rankings
Sites Building Backlinks and Onsite Blogs Perform Better
Direct Traffic From Branding Is The Key Factor To SEO
Large Websites With More Content Do Better
If You Stop Before 12 Months Then, You Screwed Up
WHAT YOU SHOULD DO
If you are considering local SEO Services, then your mental approach should be to choose a budget that you are comfortable with for the long run and I mean a 3-5 year plan. This plan doesn't mean it will take this long to get results; it just means that you should incorporate SEO as an ongoing marketing campaign. You don't want to look back three years from now and wish you started SEO, and you don't want to give up before then because you chose an overly large budget hoping results would happen immediately.
You also don't want to do SEO only and no other forms of direct brand marketing. We suggest this because this approach of expanding your marketing beyond just SEO is what our most successful customers do. Their competition wants to be like them but can't seem to fathom the idea of pushing through the beginning phase of SEO. In other words, they give up, and then they blame SEO rather than themselves while there competition benefits.