New aircraft have a much higher deprecation, even though factories try to tell you they don't deprecate, they do... they loose half their value in 5 - 10 years, depending on type and hours flown. Taking a loan for something that looses 10k per year in value (minimum) might not be the best move if you can't afford to pay back the loan+interest with at least the deprecation amount.
Deprecation is of no concern if you plan to keep it for 40 years, as by then the inflation caused the aircraft to gain in value again. But that only holds for the long term. If you buy a cheap used aircraft, that one will also gain in value due to inflation on the long term, assuming the airframe survives all these years.