Welcome to the Forum and congrats on passing your test!
What you talk about regarding your mentor and the fee split is pretty common. I had a similar thing when I was working for a small firm. We had a handshake agreement; basically whatever time I put in as a trainee, I would stick with the firm (for a fee split) roughly the same time frame. Sadly I passed my CR test right in the middle of the recession (2/2009), but either way, kept my word and stayed with the firm until I went on my own 1/2013.
As far as going on your own and/or gaining new clients when you're newly licensed/certified, yes, that can be very difficult as you are probably seeing (I did when I first got my button and even once I opened my own company - single man shop btw)
I will talk about the "Volume Guarantee" (which is what I ended up doing for a while, but has many different "titles" depending on the company/AMC you work with throughout the industry) I'll be honest, it's pretty taboo on here and you will get a lot of criticism by many members/fellow appraisers for doing it. At the time, I did it because I didn't have many other choices and was trying to establish myself and earn money for my family. Thankfully I don't deal with it anymore and have moved on to better, higher paying clients, but will admit I was one at one time who accepted low fees to get assignments.
These "guarantees" vary from AMC to AMC, but the one I had (with ACT AMC) was for $250/report (SFH) with a minimum of 15 reports per month. At the time (2013, just starting my own company) this was a huge pay raise. Again, we were just coming off the recession and I was just starting out on my own, earning 100% of the fee! So having a $40k+/yr account from one client was amazing!
Bing, bang, boom ... it got old quickly. I stayed with it for a decent amount of time, and had some other clients, but they were my "main" one because of the guarantee. I will say, they did follow through with the 15+ per month and paid on time (although I still get charged a "tech fee" for each assignment), but there was a lot of updating and follow ups, etc that went into that $250 report. I always gave it my best regardless of the fee and feel I did not do "less" because of the fee. Now, years later and having learned more and more over these past few years, I still stand by that, although will add any "shortcomings" in my reports from that time were not because of fee but maybe lack of knowledge. I've tried to (and continue to strive toward) become a better appraiser any chance I get.
I don't begrudge any appraiser who is "trying to put food on the table" or any other reason for taking such an agreement. It's all a business decision. Thankfully I can say I no longer consider anything like that at this time. No one ever knows the future, though. I will say that it gets old fast and you pretty much are seen as an employee/staff member, but without the health care benefits, 401k, etc. I'll never forget one day calling in to update that I wasn't going to have a report in that day. It was first thing in the morning (9am ish) because I was so sick and couldn't stand up without getting dizzy, let alone sit in front of a computer and finish a report. All I got was "Ok, but when can we expect it?"
Being on here (the Forum), hearing/reading others saying they say NO to such fees/agreements, "find better clients" and many other similar type posts...although frustrating to hear at the time and at times did make me feel a little like a "traitor" to the profession (undercutting other appraisers in my area on fee), did make me also ponder what these other "better clients" actually were. I can say that in the past few years, once I did sign up with other AMCs or direct clients and stated my fee was $300, $325, $350 (my fees are higher than that now, but just a few years ago, that was what I was offering)... and started getting assignments for these "higher" fees, that's when I started realizing that this "guarantee" wasn't that great. It really WAS only benefiting the AMC and NOT myself or any other appraiser. It starts to hit you that, even the difference of $250 vs $300 ... every 5th appraisal you do is basically "free" to the AMC b/c they're saving that much on each report you send. $250 vs $350 is almost every 3rd report being "free"!!!
Again, I don't begrudge nor judge you if you choose such an avenue ("guarantee" or "staff" appraiser) and it may be one of only a handful of options you have right now, since you're newly licensed, but I just wanted to share my experience with you. I'm 37, so was only 32 at the time when I took on the guarantee. I don't know how old you are, but I wasn't (am not) an "old timer" (no offense to anyone on here!) but I was getting burnt out keeping up with their constant updates, etc.
All the best to you. Salut'