Charles and I run a two-man band.
When we wrote IHMN we relied on ourselves to proof read our work and, Osprey’s editor.
We had to publish an errata.
Since then we have had three friends (Mark, Russ and Dean) proof and sense read our books and, our quality has improved enormously. An up-to-date copy of MS Word can be a godsend. Its grammar and spelling capability has come on leaps and bounds and helps you eliminate many of the ‘sillies’.
We also play test our rules with our local clubs, which can be painful for the ego, but improves the games considerably.
It does not cost much to quality check your work, even if you are part-timers like us.
Quality of layout and appearance is another thing altogether. Although we would like to, we cannot afford professional artists to fill our books with state of the art graphics. So we rely on eye-candy photos of nice miniatures in nice terrain. Some we do ourselves, but many of these are given to us for free by friends and fellow gamers (big shout-out to the peerless Kev Dallimore here).
We have been paying a professional layout artist though (Millsy of Cobalt Peak Design) and this is money well spent for it is a serious skill-set we do not have ourselves.
The Ministry of Gentlemanly Warfare