It's quite true to define it as above - 'rent to cover any loan you may use to invest as well as other letting costs'.

But, one of the commonest mistakes investors make is to underestimate the on-going costs of maintaining and letting a property.

There is no big secret to getting the sums right so long as you don't overlook costs. They include:

General maintenance of a property - this can easily turn into a monthly expense, especially if your property is old.

Making allowances for fussy tenants who constantly demand items to be fixed and which require tradesmen to be called out.

Problems that you could normally deal with quickly and easily yourself, such as faulty boilers, leaking radiators, dripping taps, etc, will require the attention of a skilled tradesman in a managed property.

In your absence you will almost certainly need to have an agency manage your property - i.e. find tenants and monitor the building, etc. Allow for the cost of this.

Tax: bear in mind that your rental income will be taxable.

Legal costs - you may be unlucky enough to find yourself in dispute with tenants. If this happens and you need to take action to evict, you will incur legal costs.

It's worth making sure you're reasonably clear about the costs and expense of this process in your selected country before you buy to let.

Your costs - if you plan to visit your property at certain times of year, then allow for the cost of this.

If you plan to keep it clear of renters for a certain number of weeks a year in order to use the property yourself, again, allow for this and consider it as a cost.

If you've re-mortgaged to buy this property, you'll also need to think about how you intend to approach the matter of currency fluctuations.

Keep in mind that if you borrow in, say, dollars, and your rental income is in another currency, a devaluation of that currency against the dollar will affect your ability to service your loan. Seems obvious, and it is, but it's often overlooked.

Of course, this could work the other way around - a rise in value of the foreign currency against the dollar would make your loan easier to repay and give you more surplus income - but there is little value in planning for such happy eventualities!