Congratulations on your purchase.
I had a 1.6 Siena from 2001-2007. The ELX vesion is fairly well loaded with aircon, power windows, ABS, airbags.
The car has a beautiful DOHC engine-accelerates like no other 1.6! The engine is also relatively maintenance-free provided you give it the scheduled filter/oil changes. Might also need throttle body cleaning.
The brakes are good but feel light and squishy (even with the ABS) and this is about its only drawback.
Please check the exhaust for rust.
The mileage of about 9-10 in city and 12 on highways is about what I got. It seems to like Speed/Xtrapremium.