Board composition and dynamics after angel investment

I would doubt that an angel investment would upset your majority status - esp. since you are a sole founder (and you haven't disclosed any other shareholder owners) .

Sounds like you are looking for an advisor, and not a board member.

You can add an advisor to your board, but your bylaws / articles of incorporation must define what their voting rights are (or are not) if you do not want the advisor to have the default rights that apply to all board members. If they are only an advisor, their exposure is also minimized - but IANAL, so I suggest you have a chat with your lawyer.

There a quite a few levels of involvement an angel can have - you need to understand up front what type best suits your (and her / his) goals.

1. The angel investor is completely passive and has very little contact with the founders of the company.
2. The angel investor holds a company board seat and advises/mentors the entrepreneurs when they need advice.
3. The angel investor holds a company board seat and is the formal advisor/mentor with set duties.
4. The angel investor holds a company board seat where s/he assumes a full-time executive role.
5. The angel investor holds a company board seat and eventually becomes the CEO. The angel investor obtains a majority position in the company and controls the existing board of directors

Additional relevant info on this topic can be found here.

Your level of control will be determined by the mechanisms you use in your contract. For example, you could issue your investor with Preference shares:

preferred stock: stock whose holders are guaranteed priority in the payment of dividends but whose holders have no voting rights.

It's Mechanisms like these that will help you strike a balance with your potential investors - it all depends on how much the investor trusts you with his/her money, what(/when) (s)he is looking to get out of his/her investment and how much time and effort (s)he is willing to put in to your company.

When it comes to selling your company there are also other things to look at, like "drag along rights" which enables a majority shareholder to force a minority shareholder to join in on the same of the company.

So overall you can see there are a number of ways to ensure you have the control you desire, while still keeping all parties happy. However quite often you will find that the investor wants to lay down the initial terms and conditions and you may need to make compromises, depending on your situation. Also when looking for investors, don't jump right with the first person who is willing to part with their money. Excuse the bad analogy, but think of it as a kind of marriage, (s)he may be pretty, funny, <>... but that doesn't mean they are the right fit for you or your company.