The IRS does not treat a sole proprietorship as a "single-member". It ignores the existence of the sole proprietorship for tax purposes, as do the states (generally). In other words, you and the business are the same in the eyes of the tax codes. An S-Corp which has a single member is also treated as a disregarded entity by the IRS. However, states differ on their treatment of S-Corps. Most states follow the IRS in disregarding the S-Corp entity, but a few do not.

Fee-wise, the differences are immediate. You must pay fees to the state and federal government related to your corporate entity. The total amount depends on your state.

Tax-wise, the difference is minimal, but the S-Corp form does make it easier to take and support deductions because you will probably maintain separate records for your business. Sole proprietors are audited more frequently by the IRS because they generally do not keep proper or sufficient records delineating the business spending. States differ on the taxes they impose on business entities.

Liability-wise, the difference is immediate and substantial. S-Corps offer limited liability, meaning that generally the S-Corp's liabilities are not yours. In practice, banks won't make loans to S-Corps unless its owners agree to waive limited liability, and if the S-Corp is not properly capitalized (i.e., does not maintain proper insurance or reserves to cover liabilities) then courts will ignore the limited liability shield. However, sole proprietorships offer no liability protections--your liabilities and the business liabilities are one and the same: i.e., if your business goes under, creditors can go after your house.

Self-employment taxes: A sole proprietor owes self-employment taxes. These taxes include your social security contribution. You would not necessarily pay self-employment taxes if you use the S-Corp form, if for example, you pay yourself a salary up to the respected salary limit and properly treat the remainder of distributions as potentially self-employment income.

You really need to talk to an accountant and/or lawyer about this.