In the current context, only thing online store cannot or do not sale is alcohol or tobacco products. Actually vape and electronic cigarette is in trend right now and got high profit margin.
Also perishable goods customers prefer to buy locally for example sea food. ( high profit margin, around 300 to 400%)
Computer repair business. ( just to touch costumer computer you can charge $80 to $100.  less investment needed
specialty or ethnic store: something they cannot get or prefer not to get online. specialty or ethnic clothing for example. First thing is its hard to find online and second thing even if they find they don't know how it look on them so they prefer to try before they buy. And on these thing you can jack up the price as much as you want. Also God and goddess idols or supplies for festivals and rituals they don't look around for cheaper price.