If you are in the fortunate position of being able to afford to buy a house using only cash, and with no requirement to rely upon the additional support of a commercial lender in order to make up the shortfall of the asking price, then you need to be aware that you will be required to produce some documentation.
The reason for the need for purchasers who conclude a transaction using cash only to produce relevant documentation is to prevent, deter, detect, and catch fraudulent and criminal activity.
Specifically, many criminals seek to launder their ill-gotten profits that they have made through their various criminal enterprises by the purchasing of real estate with cash. By making a large purchase with their dirty money, they then have a plausible and legitimate excuse for having such a significant amount of wealth to their name and so this can further muddy the waters for law enforcement who are trying to competently investigate the conduct of the criminal.
That said, purchasing a home with cash is actually much easier and speedier a transaction than by paying with alternate forms of credit such as with a home equity loan or mortgage, and the level of paperwork involved is fairly minimal. Once you have identified a particular property that you are interested in purchasing, make sure that you do your due diligence, determining the structural condition of the property along with a search of the title deeds of the property.
Should both of these searches (which are entirely voluntary by the way, however, it is strongly recommended in the most emphatic terms possible) turn up no adverse results, you will then need to initiate contact with the seller and provide them with an offer.
Once you and the seller have finally reached a consensus as to the purchase price, the next step will involve the purchase and sales agreements being verified and signed by a qualified property attorney. The attorney will probably require that you provide a bank statement, proof that you have the necessary amount of funds, along with photographic identification such as passport, drivers license etc. This both confirms that you do indeed have the requisite amount of funds and that you are actually legally competent and entitled to conclude the transaction in question.
In the interests of both safety and convenience, you may want to convert either all or part of the funds required for the final settlement of the transaction into cashier checks. The benefit of cashier checks is that unlike money, they can only ever be used by the recipient and so this means that if they are stolen, they can be easily traced and the thief apprehended.
Once the settlement has been duly concluded to the satisfaction of both parties to the transaction, the deeds will be transferred as appropriate. Your real estate attorney will be better able to explain the precise mechanics involved in this specific part of the process.
And there you have it! The property is now legally yours, for you to use as you see fit.