What nobody tells you about budgeting for a flat

Noida Extension — I've been looking at properties here for months now, especially around Sector 145, trying to find my first 2BHK. Saw a few at CPA Developers Pvt Ltd, seemed decent. Honestly, I thought the property price was the main budget. Turns out, the stamp duty, registration, and then interiors add like 15-20% more! My parents keep saying factor in everything, but I had no idea it'd be this much. Also, the home loan process? So many banks, different rates. HDFC seemed okay, but not sure if there's a smoother option. Am I the only one who felt completely blindsided by all these extra costs? What other things should I budget for that aren't obvious? Any bank recommendations for a first-time buyer with good rates and less paperwork?