To buy a house, you generally need to consider several key costs:

1. Down Payment: Usually ranges from 3% to 20% of the home's purchase price. A 20% down payment is common to avoid private mortgage insurance (PMI). For example, on a $300,000 home, that would be $60,000, but some loans allow down payments as low as 3%, or $9,000 on the same home price.
2. Closing Costs: These are additional fees related to the transaction, typically 2% to 6% of the loan amount. This can include legal fees, taxes, and other administrative costs.
3. Additional Costs: May include moving expenses, home inspections, property taxes, homeowners insurance, and maintenance, which are ongoing costs after purchase.
4. Income and Debt: Mortgage lenders often recommend that your monthly mortgage payments do not exceed 28% to 32% of your gross monthly income and your total debt payments (including mortgage) stay below 40% to 50% of your income.
5. For the Netherlands specifically, you typically need about 3% to 5% of the purchase price extra for buying costs like taxes and fees, plus some equity for down payment or to cover bidding above asking price in competitive markets.

In summary, to buy a house, plan on having a down payment between 3% and 20% of the home's price plus 3% to 6% for closing and purchase-related costs, along with ensuring your income and debts align with mortgage lending guidelines.