Answer:
Limited liability company
Explanation:
A limited liability company is one that the owners are not personally liable for the business. Rather the company is a legal entity on its own and can be sued legally as a sepearte entity from its owners.
It combines features of a corporation and a partnership or sole proprietorship.
This will be the best type of business given that the business will not be expected to earn for the first two years. The sisters will not be personally liable for any debt incurred.
Also the business will continue even if only one of the sisters remains.
So an LLC is the best option for them.