Bettas can live with other fish but it really depends on the individual betta. Some are so aggressive that they can't even live with snails...others are so peaceful that they can be housed with Gouramis and Guppies (species that are normally not recommended to keep with bettas).
If you definitely want a community tank I wouldn't recommend getting a betta (unless maybe you have a plan for the fish if there are issues). Aggression problems with betta fish aren't THAT common but I figured you should be aware that it can and does happen. Sometimes it's actually the reverse...other fish nip at or even attack the betta.
Avoid Gouramis/Paradisefish...they're closely related to bettas and will often fight with them. Don't get fancy guppies either as the long, colorful fins remind bettas of other male bettas. White Cloud Minnows and Neon Tetras (most tetras, actually) can make great tankmates but sometimes they'll nip at bettas' fins. I haven't personally experienced this but many people have. Danios can work but I wouldn't recommend them as your first choice. They move very quickly and can be nippy...they tend to stress bettas out.
Platies and Swordtails usually work but some bettas act aggressively because of the bright colors.
Cherry barbs, cory cats, and bristlenose plecos (they stay small for a pleco and are great algae eaters) are great betta tankmates, I haven't heard of anyone having issues with them. Apple snails are nice if you want something a little different (they eat algae too). Some people keep African dwarf frogs with their betta but sometimes the betta will just steal all of the food.
I'm not sure why an algae eater is a "must"? It's really not a requirement at all. If your tank is prone to algae problems than something is wrong...it might be getting too much/too little light, the fish were being overfed, there weren't enough water changes being done, etc. If you definitely want a betta-friendly algae eater then look into Oto cats. They do best in schools and can be a bit sensitive to water conditions (I've never had issues with mine, though. I feel that a lot of them don't do well because of petstore conditions...mainly lack of proper food. By the time most people get them they're completely emaciated.). Acclimate them slowly and get them from a good store and you should be fine
. Oh, and make sure you have plenty of plants.