Definitely not recommended. Although it may not cost you anything, the result of such an appraisal of your property can cost you considerable amount of money and a lot of lost time. You will not know if your purchase price corresponds to the real market price and you will therefore waste a lot of time by offering an unrealistic selling price. That is why I do not recommend any of the so called on-line appraisals. These prices are determined without any local survey. Real estate agencies have their own or buy programs used for such estimates. They claim that they use the comparative method and, for an additional fee, they even claim that they use the actual purchase (sales) prices. In these programs, you enter only a few pieces of information about the construction and condition of your property. The comparative properties cannot be used without a thorough study and corrections. Real estate offers on real estate portals contain a lot of mistakes made by the brokers which affect your real estate price. It is very good business for the creators of these programs and real estate agencies want to acquire your property for sale.
I recommend only appraisers with a regulated trade and, if possible, the ones who are also real estate agents or have a person in the real estate agency who is responsible for this activity.