Branching Into Hardscaping

I own a landscape firm, the majority of our work is maintenance contracts, but we as well do landscape design/installs, irrigation, and lighting. I received my ICPI level 1 certification over the winter as well as my NCMA certification. A Allan Block and Belgard manufacturer invited me free of charge to attend their AB certified installer course to try and get me into their products. (I learned more in the AB class than I did in the NCMA, the guy that taught the NCMA was an engineer and admitted he never installed the first block, so it was just an akward class and he just assumed everyone knew all the material instead of actually teaching it.)

I have never installed a wall or laid the first paver, I know when I start a few jobs it will be rough and will probably be constantly referring back to my literature from class to make sure everything is being done correct.

My best friend who has been in the mowing only business for 15 years and does great work, he also was partnered with me in my current company when it was young, but only until he got his degree. He currently lives about 50ish miles away and is a high school algebra teacher. He loves mowing grass and is looking for some extra cash so he is starting a small mowing business in his town. He only wants to cut grass and doesn't want to do anything else, he starting passing out a lot of cards yesterday in his town in these mid-high end residentials and people have asked him about landscaping etc. he told them he is only cutting grass on the side but gives them the quick run down of my background and gives them a high recommendation to call me. He has given me 3 prospect good jobs in just one day of passing out cards for himself. 2 are landscape projects and 1 request for a wall.

I am looking for advice on how to start/branch off into the hardscape industry without low-balling, I know the first few jobs the planned profit will get dried up from getting in the hang of things. I have been applauded by other guys for starting off right by getting the certification and correct education, I have just been nervous on marketing that we do walls and pavers and that I might miss something on a job for being new, screw it up, and our companies name and reputation for all of our services is screwed up for messing up a job.

I don't know... just any advice for me on anything for starting or in the hardscape industry would be appreciated