They are actually trying to give you some good advice. It's just that we have a lot of "hacks" in this industry that work without insurance and don't pay taxes. We're all getting tired of it and quite often there's a good amount of sarcasm in the posts.
Many of the nationals are finding new people to do their work at the lowest prices because the vendors who have been in the industry KNOW what the prices are.
At $18 - $20 per lawn, they are making a killer profit off of you and, in return, they will expect you to do initial cuts on properties that are way overgrown and are between 5,000 to 15,000 sf. Maybe larger.
When you refuse to do the cut because the pricing isn't fair, they will bully you into doing it by threatening to charge you back. Problem is, the chargebacks will end up being MORE than what they are offering you to do it for because they will have to go to an experienced vendor who will end up bidding it.
You will have some companies tell you that before, DURING, and after photos are required or you won't be paid. If you work alone, you cannot take a photo of yourself mowing the lawn, trimming bushes, or using the weedeater.
If you want to get into this business and make any money at it, I suggest you read everything at both of these threads:
There's a LOT of great information there, including reviews of companies that burn people.
Should you decide to go forward with these types of cuts at these rates, I wish you luck. I would really suggest reading and participating first, however. We don't want to see a newbie taken advantage of anymore than we want to be taken advantage of.