I am trying to display a select list from a custom controller, and i get a "Read only property 'productsTitle'" error when trying to save the visualforce page.

My custom controller:
 

public class BpmIcountPayment{

    private final Account account;

    public String productsTitle {
      get { return 'products for sale'; }
    }
 
    public BpmIcountPayment() {
        account = [SELECT Id, Name, Site FROM Account
                   WHERE Id = :ApexPages.currentPage().getParameters().get('id')];
    }

    public Account getAccount() {
        return account;
    }

    public List<SelectOption> getProductsLov() {
        List<SelectOption> products = new List<SelectOption>();
        List<Product2> productsList = [SELECT Name, Family 
                                      FROM Product2 
                                      WHERE (Family = 'ShopProduct') 
                                      OR (Family = 'CourseParent') 
                                      OR (Family = 'SFCourseProgram')];

        for (Product2 currProduct : productsList) {
            products.add(new SelectOption(currProduct.Id, currProduct.Name));
        }

        return products;
    }
}

And my visualforce page:

<apex:page Controller="BpmIcountPayment">
    <apex:param name="first_name" value="Account.FirstName"/>
    <apex:param name="last_name" value="Account.LastName"/>
    <apex:param name="id" value="Account.idnumber__c"/>
    <apex:param name="address" value="Account.Address"/>
    <apex:form>
        <apex:selectList value="{!productsTitle}" multiselect="false">
            <apex:selectOptions value="{!ProductsLov}"></apex:selectOptions>
        </apex:selectList>
    </apex:form>
</apex:page>