Hi Craig and

.
I started with a cheap $50 4.5" nearly a year ago and was amazed at what I could see including Nebulae ( have a look at Orions Sword ), Globular Clusters ( Omega Centauri and 47 Tuc) and planets, (Mars, Jupiter, Saturn and Venus so far).
I've since built a 10" Dob, started astrophotography and rebuilt my 12 x 50 binoculars. I am now awaiting a big solid EQ6 Pro mount to arrive so I can re-use my 4.5" as an Astrocam after modifying it for even better viewing.
Nothing wrong starting with a 4.5" but be warned it can rapidly lead to aperture fever and dissappation of your wallet contents. The folks on here will happily help you acheive that state with maximum enjoyment. And get Stellarium, a free and excellent learning tool)
( Have a look at Orions Sword asap, it will soon be gone till next year )