It really depends on two Main things, the first being what is the online business, and the second is what is the attitude of the owner.

You want to invest less than 100k per investment, and want the original owner to continue the work.

The online world is a completely different one to the brick and mortar one. Experience in running online businesses is something that only comes with endless hours trying to build an online brand.

My recommendation would be find the Niches or Products that you really believe in. Check out their website and their company history. It only takes a little bit of research to find out who is behind an online business. Then its as simple as making an offer for a share of the business revenue.

Another option would be to look for automated online businesses, there will be a lot of them, that make a regular income through a product or service. Calculate the return you want and purchase one of them.

However, if you want a partner that will be working on the business you need to find someone that is really passionate about what they are doing. Only those people have the motivation to keep going when things are going against them.