Hi,

Definitely don't hire someone! This is easy!

The way I see it you have two options, you can either install edging, or use a garden spade or sharp shovel to maintain an edge to the bed. Installing edging is simple. You can find pre-made edging at any big box store. You can choose from plastic, stone, or wood and there's endless possibilities. Just this past weekend I installed stone edging that was made out of brick pavers. I just recessed the pavers into the edge of the bed by digging the area out with a trowel and laying them down. I added some adhesive between the stones for good measure.

The edging acts as a physical barrier to prevent grass to spreading to where you don't want it.

If you want a more clean look, you can maintain the edging with a spade. Check this video out. You'll get an effect like this:

I use both approaches in my landscaping, it is all up to you and your personal taste. Edging with stone or materials is easier maintenance long term but requires more work up front. Hope this helps!

Swapnil & baconquest, you both have different types of grass. Swapnil's grass will walk across any barrier. Those runner (stolons) can get 10 ft long and walk across roads & climb walls - I can see them starting to cross your sidewalk. Keeping a clean edge with an air gap (several inches of space from the top of the grass down to the mulch) like in bacon's 2nd picture would probably make it easier to trim the edges when you mow. You can try to put in a 1 foot tall wall, but the runners may still go over or around it.