Imo, appraising might work part-time for retired or semi-retired. For anyone else, why bother if you can not make enough full-time income from it? Do something else.
PDC collection pays too low to count except as a side gig. And even there, it's questionable.
RE sales is extremely competitive and requires an extrovert sales personality ( which most applicants lack.) Appraisal and home inspection are the best match - . Multiple licenses cost a fortune to maintain and time every two years, taking mandatory CE, plus a part-time employee is competing against full-time employees, who are better positioned to get and maintain business.