From www.irs.gov - specifically hobby loss rules for all the "business" owners:
In general, taxpayers may deduct ordinary and necessary expenses for conducting a trade or business. An ordinary expense is an expense that is common and accepted in the taxpayer’s trade or business. A necessary expense is one that is appropriate for the business. Generally, an activity qualifies as a business if it is carried on with the reasonable expectation of earning a profit.
In order to make this determination, taxpayers should consider the following factors:
Does the time and effort put into the activity indicate an intention to make a profit?
Does the taxpayer depend on income from the activity?
If there are losses, are they due to circumstances beyond the taxpayer’s control or did they occur in the start-up phase of the business?
Has the taxpayer changed methods of operation to improve profitability?
Does the taxpayer or his/her advisors have the knowledge needed to carry on the activity as a successful business?
Has the taxpayer made a profit in similar activities in the past?
Does the activity make a profit in some years?
Can the taxpayer expect to make a profit in the future from the appreciation of assets used in the activity?
The IRS presumes that an activity is carried on for profit if it makes a profit during at least three of the last five tax years, including the current year — at least two of the last seven years for activities that consist primarily of breeding, showing, training or racing horses.
As far as tax write-offs for equipment (depreciation) a taxpayer can elect to take section 179 depreciation max of $500K (new or used), or sec. 168 bonus depreciation (new equipment only with no limit), reported on form 4562
Subsequent asset sales are subject to re-capture rules. (you have to report those on your income tax returns form 4797)
7d, 100-400L, 17-40L, 24-105L, 85 1.8, 50 1.4, 580exii, 430exii, AB 800, reflectors/lightstands/modifiers.