If say i can't get a job in an agency and start my own, can i start small and then when i get members move into something bigger like the mansion? are there any drawbacks to starting your own agency?
yes; the only draw back i see is that usually it takes a good amount of time and patience to go through with that, although i'm sure you can find a job within another agency
Just be upfront with whoever you think of joining with that you want to start your own one day.
You can always move your agency.