Due diligence, legal work on both sides of the border, escrow costs, state and municipal licensing for arboriculture and pesticide application, insurance, and the working capital the business needs after closing. Confirm any government filing charges against the current published fee schedule rather than an estimate.
Count the money that is spent but not invested
Buyers build a budget around the purchase price and then discover a second budget that produces no equity at all. Due diligence on a service business means an accountant reviewing three years of statements, a lawyer checking the vehicle titles and the customer contracts, and somebody verifying that the spray licence transfers or must be reapplied for. Escrow and closing costs follow.
Then there is licensing: arborist certification, pesticide applicator licensing, contractor registration and commercial vehicle requirements are all state or local matters and none of them are handled by an immigration filing. Insurance for tree work is not trivial. Working capital is the item most often forgotten, because payroll continues from the first week while receivables lag.
Where an application fee or a petition charge applies, take the current amount from the published schedule. The useful discipline is to separate money that becomes part of the enterprise from money that is simply consumed getting there, because only the first counts toward the investment.