While a letter of intent to purchase a house does not substitute for a legal contract, writing a letter of intent to the home's seller can both assure her of your strong interest in purchase and help you both work out any issues that may come in the way of a successful sale. In a letter of intent, you can use ordinary language to state the conditions under which you plan to buy the house, specify any terms that can affect that purchase, establish agreement on the purchase price and take steps to expedite necessary legal steps that must be taken to conduct the sale.
Contact the home's seller and arrange to discuss the terms of your letter, if possible. Take notes and offer the seller the chance to do the same. During your discussion, you can identify the issues on which you already agree and try to work out those on which you do not. If you cannot contact your seller directly, find out whether information can be exchanged through your real estate agents or in some other way. Your goal is to remove all obstacles to your purchase before a contract is drawn up.
Make an outline of what you need to say. You can write it out in plain language or keep the letter in an outline form. You need to include your name, the address of the property, your purchase offer (that can include the down payment; the time you need to get a loan; the time when you go to contract and closing) and anything else that affects that process (repairs that determine the final price or purchase; results of housing inspection; your failure to obtain the job that impels you to buy the house). Keep small issues on your outline (there's a broken pane in the kitchen window; peeling trim on the back door might be caused by a leak, but you don't know yet), but reserve these to talk about with the seller first. Unless the colour of the dining room is an absolute deal-breaker for you, it's just part of buying a house.
Protect yourself and your seller by adding a line that says you both know that this is not a binding legal document, just an agreement on your intent to buy the house. Add a line at the bottom for each of you to sign and date the letter. Each of you can keep a copy.
Use your legal name--the one you use when you do business--and your current address to say who you are. Use the full address of the house you want to buy: 155 Alder Street, Greenway MD, rather than just 155 Alder. You can add "the two-story ranch house" or another description of the property if you want.
Be very clear about problems that must be solved before purchase can happen. After your discussion with the seller, you may be able to label some or many of these "We agree." For example, Mr. Jones must have a new roof put on the garage before sale. Mr. Jones has already shown you three bids on the roof and told you he can only afford two of them. In discussion you may have worked out that you want the third company and will reimburse him £520 to get the job done by that company. That is an item you can label "We agree," and that agreement belongs in your letter. The house must be inspected: Put in the letter that the sale depends on a successful inspection. You are moving into an area where there are frequent tornadoes. You can put in the letter that you will not buy the house if it is damaged by a tornado between now and the sale.
Be clear about non-property problems that will affect the sale. For example, the house you want to buy depends on your being transferred to the area. Put that in the letter. Some large general issues are assumed; if you cannot sell your old house and find a loan to buy the new house, clearly it isn't going to happen. But a job transfer is a specific problem that has an affect on you.
Distinguish between problems that validly belong to the purchase and those that do not. Inspection reveals dry-rot. That is a structural problem affecting the value of the property and a high repair expense that could not be anticipated. Problems found in inspection also affect insurance. This is why you want to say in the letter that the price you have offered is dependent on a successful inspection. Some problems are just problems. You pass the house one day and notice that the beautiful green grass has some brownish patches. Yes, there's granite under part of the yard, so the brownish patches always need extra watering when it gets hot because the soil's thinner over the rock. There's no law saying all the grass has to be the same green; leave it out of the letter and buy more hose.
You don't have to be a lawyer to write a letter of intent and you don't have to sound like one. Talking with your seller and laying your letter out in plain language are all you need to write a good letter of intent. Your seller will be glad to know of your solid interest. You will still need a formal legal contract to purchase the house, but it will be much easier and clearer to produce if you have organised your thoughts in a letter of intent.