HOAs can prevent you from building an ADU. While it may be frustrating to have someone regulate what you can and can't do to your home, try to remind yourself of what the HOA wants. HOAs want to make neighborhoods uniform and tidy. Therefore, even if your HOA turns down plans for an ADU, don't just give up. Contact the HOA and see if there is anything else you can provide for approval. Another scenario is that the HOA may approve your plans but with costly restrictions. If you live in an area with an HOA you should prepare for obstacles they may place in the way. You may want to consider whether the HOA will enforce changes to your plans that would increase your cost, and what this will mean for your loan amount if you choose to finance the project.