First of all, you will need to think of a business plan BEFORE even thinking about choosing a partner. Think of something that will make you unique. Something that will attract people to you. Unless you're unique, you will NOT make money. The market is just too saturated these days. When you go host hunting to try and locate your upstream provider, take many things into account.
1) Durability - How long have they been in business. If it's less than a few years, don't even bother.
2) Reliability - What is their uptime? Anything less than 99.9%, don't bother. Their downtime will be YOUR downtime too.
3) Overselling - Do they offer unlimited plans? If so, move on. Avoid "oversold" servers and stick with somebody who has specific plans.
4) Price - Look for somebody who offers decent plans at a decent price. Plans that are "too good to be true" usually are. Avoid price gougers too.
5) Network - What datacenter do they use? Is it a prime datacenter, or a budget place? This make a big difference in spead and reliability.
6) Hardware - What physical hardware does the reseller use? What CPU brand and speed. Ram. Hard drive speed and type. Network uplink.
All of these are factors to look into when choosing an upstream provider. If they want your business, they'll be willing to share this information. Those who are reluctant to share, are usually shady or just another reseller themselves. The right combination of: uplink provider, plan pricing, and your target market will make or break you on the reseller side of things.