Shared Ownership Cost Calculator
Add the mortgage on the share you own to the rent on the share you do not, plus service charge, for the real monthly cost of shared ownership.
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Part-buy schemes lower the deposit needed by selling you a share and charging rent on the rest. The monthly cost is therefore three things at once — a mortgage, a rent, and usually a service charge — and comparing only the mortgage against a normal purchase makes it look far cheaper than it is.
Rent on the unowned share typically rises annually by an index-linked formula, so the total cost climbs even on a fixed mortgage. That escalation is the part most buyers do not model.
The calculation
Your share costs the full value times the percentage bought. The mortgage is that less your deposit, priced over the term. Rent is charged on the value of the share you do not own at the annual rate in the lease, divided by twelve. The service charge is on top, and it is normally charged on the whole property, not your share.
Worked example
On a 300,000 property, a 40% share is 120,000. A 10% deposit is 12,000, leaving a 108,000 mortgage at 6.5% over 25 years — about 729 a month. Rent on the unowned 180,000 at 2.75% is 413 a month, and a 120 service charge brings the total to 1,262.
Buying more of it costs more than you expect
Increasing your share is priced at the market value at that time, not what you originally paid, so in a rising market each step costs more. Add valuation and legal fees for every purchase, and check whether the scheme permits reaching full ownership at all.
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Create your free property pageFrequently asked questions
Is shared ownership cheaper than buying outright?
The deposit is much smaller, which is the point. The monthly cost is often similar to or above a full purchase once rent and service charge are added, and you own only part of the asset and its growth.
Does the rent go up?
Almost always, usually annually by an inflation-linked formula set in the lease. Over a long period that escalation can be substantial, so read the review clause and project it forward before committing.
Can I sell whenever I want?
Usually with restrictions. Many schemes give the provider a period to find a buyer first and set the price by independent valuation, which can make selling slower than a normal sale. Check the resale clause before buying.
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