well... keep the repair service... take on an extra hand if needed... theres a cheap way to do it too... employ a youth as you can legally pay them less
in the UK its like 15-18 a set figure or something like that and then 18-25 a certain amount and then above 25 the max minimum wage per hour... someone will correct me on this eventually as I am running from memory of several years ago now...
But yeah theres more than one way to develop software to ensure future income...
quick examples include... if they want exclusive rights to the software... charge them your estimated value for a period up to 10 years.. or five to be fair... and if they refuse to buy the rights of the software then you can keep resell rights to rework the projects for other clients... so think laterally not linear

[remember to contract and paperwork everything!!!]
hope this helps you move foreward...
also you can sell for cheap... but charge for updates too
so look at your income possibilities and expand on them any idea is an idea...
Always happy to help motivate you when needed and if you need someone to talk to about this... you got me and this forum anytime