There are ways to deal with this to minimize the transition and adapt new animals or other species into the home, but you should consider your household as it is now and what you feel will be the reactions of your established pets. Quality time with animals is more important than quantity. Some animals like to hang out with you while others will want to engage in play activities or excursions. It is not fair to add more animals if you think you will be unable to give them proper attention, care, and love. It is also incorrect to think they will entertain each other.
Animals are a big commitment.
The more you have the more resources they demand. This is critical to a multiple animal household. Sometimes you may want to have tests run and make sure all the vaccinations are done. If not you may introduce parasites, disease, or infections to your current pets. If yes, then read more about integration.