My first recommendation would be to reach out to companies that are already set up and see if you can work for them as a teacher. Dumb Ox Learning specializes in AP courses and Homeschool Connections offers all subjects from 3rd-12th grade. There are several others as well -- I think Memoria Press offers online classes, but I'm not sure if they cover every subject.

It's obviously more difficult to do everything yourself, especially when trying to connect with families needing your services, but I do use a similar service for my own children. What I look for the most is (1) a class that I can't easily direct myself and (2) something that would be equivalent to a full high school credit which is typically about 30 weeks worth of instruction. The great thing about teaching an entire course is that you get to choose the curriculum you prefer to teach.

Another option that I've seen is to set up an entirely online, self-paced course with prerecorded video lessons and then sell the course year-round. There are many students who need to start new classes at irregular times.

I'm not sure how great the demand is for online tutoring because there are many places such as a local library where you can access that service for free.

We didn't use any of the pre-packaged programs for homeschool, for all grades (Grade 6 through Grade 12, which we're in right now) I have written our own course of study, adherent to at least minimal state requirements, and purchased texts à la carte.  Our state requires affiliation with a homeschool group, and we have perhaps the most low-touch group possible in our state, you simply submit a list of basic texts for each year which they keep on file, and are free to pick whatever texts you wish.  I do have to maintain all records and transcripts myself (I wrote spreadsheets for this that closely resemble those used by schools), and they do not issue a high school diploma, that, too, is the responsibility of the homeschooling parent.

For our homeschool (just my son), we used the Holt series for science, specifically, life science, earth science, and chemistry.  Holt has abundant resources on CD-ROM, though the used copy of the chemistry text didn't come with CD-ROM and I had to write my own tests.  For life science (biology) and earth science (basically geology), I never wrote a single test.  The series is fairly weak on evolution, the theory is there, but is treated as something short of dogma, and there is a lot of "may", "possibly", "probably", "scientists think", and so on.  We tried using a Charlotte Mason text for middle school science, but I found it very puerile even for an 8th grader, so we didn't continue with that.  I also got a Thames and Kosmos chemistry set, Chem C3000, top-of-the-line, but didn't particularly care for it, as you ended up having to get a lot of supplies yourself (some ordered online) even though I thought the set would come with everything you need.  (There were about 20 different chemicals provided).  The manual appears to be translated from German and is somewhat dense to read.

As for math, we tried Saxon, and if you go through that series from soup to nuts, you will be totally proficient in math.  However, the workload is massive, and more than we could handle with juggling five or six more classes, so we jettisoned it after Grade 7 (used the Math 7/6 text and spread it over two years, and even then only got through about half of it).  Saxon presupposes that you have a lot of time to spend on math, kind of like teachers who seem to think "my class is the only class you have" (ever have a teacher like that?).  We ended up going with the Sadlier Oxford series for Algebra Fundamentals and Algebra I (Sadlier really needs to get out of the religious books business and stick to math), which had a far smaller workload, but also tended to get deeper into the weeds than was really necessary.  It's an entirely adequate series, if you can find it, I'm not sure if their math texts are in print anymore.  We finally discovered the Cord series, which we used for Algebra II and are now using for geometry.  It is very good in that it strips down math theory to its bare bones, and can be taught at any level of skill.  For our purposes it's entirely accurate.  Cord's emphasis is upon practical, real-world application of math, and again, you can teach it at any level you wish.  Neither Sadlier nor Cord come with pre-made tests, you have to write your own.  I got both of the Cord texts used.

One caveat about the Cord series, for Algebra II, I got a sample copy (really not supposed to be resold) from a thrift shop, and it did have typographical errors here and there, including in the correct solutions to problems.  For this reason, I could not ethically resell the book, as I do not have time or inclination to go through the entire book and look for errors.  I would have every hope that the final copies of these books have been vetted for errors.  This didn't affect the teaching of the theory itself.