What are the best low-investment business ideas?

Low investment business ideas relates to usually business like private tutions, academic consultations, Fitness and Diet trainning consulting or any business based on commission basis.

Most of the above stated are conducted in cafes with one laptiop with no rental office cost or furniture involved.

skills ...as that guy said if you are good at something never do it for free that is the cheapest advice i can give you ....what are you good at and how you can market that 

the one that are knowledgable form the clientele as it will reach them quicker which avoid heavy concept investment and lower marketing which means quicker turnover

Consultancy Services are most profitable and low cost business as the commodity offered is Services and just requires a basic business setup to Comply with Local Government Requirements.

Can be started with a One man show and proceed as per market demand

It depends on economies. Say for example in India we may even start business by few thousand Rupees for exapmple creating self help groups for making spices, using waste cloths for creative artifacts.

In modern context making an innovative website/ mobile app may prove extremely good business idea.

The best low investment ideas is selling products and services online like network marketing, travel and energy.

Online Marketing of FMCG and electronic items

Where you have unparalled knowledge of your industry of which companies require. Oil an Gas consultants, shipping, construction. In fact all industries as long as you no more than the company hiring you does. Thats where your unique selling point kicks in. Or take on business aspects that a company would prefer not to hire for as it maybe a short term contract.

ideas with service products are always the low-investment ideas 

I think best low investemant business is to purchase simlpe itams from hole sale market and sell in retails market this is batter idea