Water line break on your property-

[OMG!WTF!]

I'm not sure checking the slope of your drain is a good idea either unless you're trained on what to look for. Too much slope is just as bad as not enough. Tricky stuff for a home owner to get right.

[blender]

As it happens this occurred in my front yard two weeks ago. No insurance coverage as it did not damage the house and I wasn't carrying a specific endorsement to cover it.
It was chaos, but fortunately I work for a general contractor and was able to bring in an excavator operator and a plumber I know who treated me very fairly. My costs other than my own time and a bunch of DIY landscaping that is ongoing was about 1200 bucks.

I'd say retail shouldn't be more than 5k tops. We had 100' of line to replace and we did the sani as well.