If what you want is a quotation or offer, then sending a letter of intent makes you look ignorant while requesting a quotation will generally at least make you look like you know what it is that you want. And what you want, after all, is a price quote. Hence you want to request a price quote, via a request for quotation.
Using Letters of Intent With Real Estate Agents. Some real estate agents and real estate brokers prefer to write up a contract for each offer, while others use a letter of intent to express interest in a property and to work out the details before writing up a full contract to purchase real estate. Many bank owned properties (also known as REO properties) are explicitly telling agents not to submit letters of intent on their listings, but with private sellers, a letter of intent can be a good way to introduce your creative offer to a seller without a huge amount of time invested by your real estate agent.