This area is tough, there are a lot of small guys running around doing things like this already but then there is still demand. I don't see the OP getting rich off this but if he can keep his budget in line and do side jobs as he gets them he could make some extra money while enjoying the outdoors.
While I didn't expand too much in your other thread dealing with what size excavator I will add a little more to this one. Drainage work is great if you have helpers checking the grade for you. It keeps you in the seat and making progress. If your going to try doing things like this by yourself you will find it very frustrating hopping in and out of the machine every 10' checking grade. You can go with a laser setup of find an old style transit (will be much cheaper but need two people to be efficient to run this style).
I already covered the stump issues, concrete can be even worse then stumps. I just had to dig a drain line for a job site and the line was entering the building at an old window well that was filled with gravel. I dug as much gravel out as I could and started trying to work the concrete loose. It ended up being almost 2' thick on the bottom as they dug the hole, formed up the inside and poured the concrete from the form to the dirt. Had to use a Cat skid steer and lots of blocking to get it out. My mini could start to lift it but it was too bulky to really be able to get out of the hole. I could have dug a deep hole next to it but that would have been admitting defeat. When it was up high enough we put the skid steer bucket under one edge and I backed up while holding the other side. Drop the blade and was finally able to pull it onto the surface. Then used the skid to push it out of the way. I never expected it to be that big. It was almost worth getting the demolition hammer and breaking it down but again, that would have been admitting defeat.
Small ponds and such are fun projects. Charge by the hour though that way they can have you dig till their pockets are happy. Digging a pond with a mini (or any excavator for that matter) can be a challenge as you need to keep moving the spoils away. You will find it very frustrating as you spend more time moving spoils it feels like then you do digging the pond.
I have a friend who has a full time job but he does small projects on the side. He has a 3 ton mini he uses for drainage projects, a small dozer and small loader tractor (small Kubota 30 horse unit). He stays very busy just by word of mouth doing small projects for people. He knows what his equipment can handle and what it can't and he isn't afraid to turn down projects that are too big or too much of a hassle. He makes some extra money and it helps him to keep adding to his toy fleet but it isn't his sole income. Try to find your nitch and build up slow. If you have very little excavator experience it will be easy to cut your own throat bidding. Try to pick jobs that pay by the hour till you get enough experience to better bid a job. And remember, bidding an excavation job is a gamble, you never know what your going to hit under ground till you start digging. And remember, 811 is your friend. Call them anytime you dig and always be careful.
Ill try to expound on your comments from each paragraph (btw thank you once again for going into detail on another post, it is all very very helpful)
When I do excavate, I would have 1 or 2 other workers with me, and if its drainage they would have to keep a constant grade for me as well, i dont want water flowing uphill haha, and i would hopefully be able to find an older style transit that would do the job just fine, in regards to depth.
Also in response to how you took out that big concrete slab, I have almost identically did the same thing many times when I used to do blacktop and we had to dig out the old concrete driveways. You have to wiggle and shake the concrete chunks with the excavator while lifting up the edge with the skidsteer bucket, and just try to pull the chunk out as well as possible.
But you said that you could have dug around it and just pulled it out with the mini, but you didnt want to admit defeat haha
I would love to do work on small ponds, creeks, other bodies of water etc... I talked to my dad about it today and he also said charge by the hour so i could dig until the client is happy with the job.
--On that note, I would have to keep the dump trailer by the excavator the entire time im digging out, so i wouldnt have to worry about cleaning up piles of dirt/mud/etc later right??
--Your friend who does the excavator job on the side from his full time job is what I want to do, start off with craigslist and word of mouth at first. It looks like he has quite a small fleet though (mini ex, small dozer, small loader) so his job opportunities are probably much mire open than mine, unless I choose to rent some equipment for bigger jobs.
I have alot of construction experience, but little operating experience of an excavator. So I would only bid on jobs that I could handle and have some knowledge of as well.
Also you recommend that I only bid on pay by the hour jobs? Ill make more/less that way, or its just better to do before I bid on a contract job (1 payment)