So you made 5k and 4k per month consistently? If this is true, tell me what your secret is. Did you make that money from parking revenue?
Not from parking but from domain sales, gross much higher, though its average per month, so some months i made more than 5k some less than 5k but overall average should be around 5k. not counting my recent 30K sale. august was my best month. 13k+ net november worst 2.5k net. net income not only depends on sales but also my expenses of renewals, transfers, purchases or new acquisations, in the last quarter i have maximum renewals.
There is no one secret but here i will mention some of the points i follow -
try every possible niche like geo, brandables, liquid or others so that you don't be dependent on any single niche.
though most of the names i have are .com but i don't shy away from trying net org or .co or .in and more
keep yourself updated with namebio or namepros reported domain sales thread and other possible sources to know whats selling.
Keep up with latest tech and startups, who and whch niche is getting most funding, whats trending etc.
make good use of dropcatch discount backorder.
when there is any promo offer for handreg try to bulk register during that period.
GD closeouts one of better source to get quality for nominal price. though lots of competition now and its getting difficult but still if you focus you can get good names.
if you check aftermarket also its tough to get any name for fair price but if you keep trying then there also you get chance few times to get a good deal.
try to check around your network or social media that whether you are getting any good deals to buy domains.
rarely but you will even find names at dan, sedo etc that can be worth buying.
for selling - afternic premium listing has been the biggest source for me. So i make sure to avoid registers that are not eligible for that. parking at dan and now epik work fine for me. and Previously i have used efty which was good as well.