So, how does the immigration work ? The key requirement is that you need to maintain your H1B Visa status. The only way to do that is be employed full time and then study as part time. You will need to work full time for 40 hours as per the required conditions of H1B Visa. You can take classes in the evenings and continue your education. You can also take classes in the weekend and study on H1B Visa.
You can take as many courses as you want, as long as you can maintain your H1-B visa status in the US. Usually, it is common for working professionals to take about 6 credit hours for studying during h1B. Some tend to take even less courses depending upon the load. Some may try to take more courses like 3 of them summing up to 9 credit hours, which can be a lot of load and hard to manage with H1B. Nevertheless, it is up to the student to manage the load.
Also, as you are not on F1 visa, you will not get any I20 or anything as such from the school. You will need to mention that you are on H1B and supply the required documents like approved I-797 form and your current status details with I-94 to the admissions department.
Did you study on H1B ? What are your thoughts ?