ALL the Four Thirds lenses are relatively inexpensive. When I shot that system I had a 40-150, a 70-300, 50-200 f/2.8-3.5, an 18-180, 1.4X and 2X teleconverters. They all render beautifully, warmer than M43 lenses.
I was looking closely at the 70-300, which I've seen in the $150-$300 range. I like long lenses - I bought my m4/3 75-300 on sale even before I decided which camera I would start with! I've heard good things about the 50-200 SWD, but it's not exactly inexpensive. Probably also outresolves the 10 MP sensor by a lot too.
Remember, the E-4xx cameras don't have image stabilization in the camera. As you add telephoto lenses, either lens based or sensor shift stabilization becomes more important unless you can shoot at 1/600 or faster on the long end.
I've not used the E-410, but there was a bit of a learning curve when the E-510 came out to get decent pictures (I had pre-ordered the E-510 when it was announced, and I got one of the first copies of it in the USA):
- The E-510 goes down the ISO 100, but the sensor seems to be more tuned towards ISO 200. If I shot at ISO 100, I tended to get slightly under-exposed photos, while ISO 200 was better exposed (if a little bit noisier). There was a feeling among the E-520 early adopters that the base ISO was really ISO 125, and Olympus didn't really adjust the metering settings. IIRC, you did not have partial ISO stops in that era, so you only had ISO 100, 200, 400, etc.
- The E-510 split normal matrix metering (ESP) into two types (ESP and ESP+AF). The default is ESP+AF, while previously the cameras used ESP meter. Unfortunately, they hid the ESP vs. ESP+AF setting in a second level menu, rather than making it an option in the main meter menu (ESP, center-weighted, spot). Most of us that were upgrading from previous Olympus cameras missed this. When I went and de-selected ESP+AF, my outdoor pictures became better exposed.
- I tended to feel that the JPEG engine produced pictures on the cool side, and I needed in post processing to lift the JPEG tone curve a bit to get the images I was expecting. When I upgraded to the E-3 later, the camera returned to the normal Olympus colors.
In terms of the 50-200mm vs. 70-300mm, the 50-200mm produced better images, but the 70-300mm wasn't bad. I did have the EC-14, which made the 50-200mm's range close to the 70-300mm. The 50-200mm is heavier than the 70-300mm. On my E-x cameras, it balanced pretty well, but I imagine on a lighter camera like the E-410, it would be lens heavy.
There are 2 versions of the 50-200mm. I have the first version, but I used the second version when my first version was being fixed. While the speed of focusing is said to be faster with the second version (50-200mm SWD), the lens hood on the 50-200mm SWD was a serious drawback. I tend to have a rather tightly packed shoulder bag. The 50-200mm mark I fits in nicely. The 50-200mm SWD does not, because the lens hood is so wide.
If you have an E-x (E-1, E-3, and E-5) body, I can testify that the 50-200mm is splash proof. I have shot in various rain storms with it, taken it on the boat ride at Niagara Falls, etc.
The 70-300mm has a firmware update to allow it to focus better on contrast detect systems like micro 4/3rds. This means on cameras other than the E-m1 mark I or II, the focusing is now slow rather than dreadfully slow.