yep, that’s not a free service..
there are infinitely many ways to mess up the valuation for a plain vanilla swap if you are just following some textbook instructions for the first time, starting from day conventions to compounding to amortization of the notional to who knows. i suggest the first few times to rely on bloomberg and recreate the analysis to make sure your model agrees 100%. but if you dont have access to it, don’t know other sources unfortunately..