Having worked on the SMB billing and accounting space for 2 years in India - its a really really tough space to monetise profitably. The market size seems huge from the outside but its a tough nut to crack.
The space is also hyper-competitive now with khatabooks, dukaan etc spending 100s of crores with no revenue.
Its seems like what you are building is a mini-ERP for SMBs in India. If you are touching AP, AR - do you have tally integration? Pretty much every SMBs auditors will ask for it.
All the best!